Operation and control means and control arrangement for independently movable device with electric drive

The invention relates to an independently movable device with electric drive according to the preamble of claim 1.

The invention also relates to a control arrangement according to the preamble of claim 13 for an independently movable device with electric drive.

In the prior art there is known, from the patent publication US-5, 794,422, an independently moved and driven electric drive device for cutting grass, which device is provided with wheel-operating one or several electric motors. The operating time of the device is extended and the charging of the batteries made easier by providing the device with a combustion motor and a connected generator for charging the batteries. In addition, the mower includes alternative hydraulic systems. The electric control unit is realized by means of a microprocessor.

The problem is that the weight and frame measures of the mower are increased when it is provided with a combustion motor, its fuel tank and a generator. Another problem is caused by the noise created by a running combustion motor. Yet another problem is that the mower uses both fuel and possibly hydraulic fluid which are substances dangerous or at least hazardous for the environment.

Yet another problem results in that the electric motors and gears operating the wheels are mainly separate units that must be fitted together in order to ensure a reliable operation. In addition, AC-current electric motors and frequency modulators must be provided with suitable sensors in order to obtain sufficiently accurate information of the rotation speed and its fluctuations in order to give reliable speed instructions.

In said publication, a fixed seat is arranged for the user of the device on top of the device frame, and in the vicinity thereof there is provided a control support arm fastened to the frame, said arm including a steering wheel for steering the device. A foot deck provided with drive and brake pedals is arranged below, in front of the frame seat. Thus the control and operation arrangements are realized in a traditional fashion. The problem is poor ergonomy. It means that for instance sitting down on the seat and rising up again is cumbersome, because particularly the fixed control

support arm forms an obstacle both when rising up from the seat and when sitting down.

The object of the invention is to eliminate the drawbacks connected to the above described electrically driven and independently movable device. Another object of the invention is to realize a new electrically driven and independently movable device that is suited to be used as the chassis in particular for light machinery such as arrangements meant for the care and maintenance of lawns and courtyard areas.

The electrically driven and independently movable device according to the invention is characterized by what is set forth in claim 1.

The control arrangement according to the invention for an independently movable device with electric drive is characterized by what is set forth in claim 13.

The dependent claims represent preferred embodiments of the invention.

The electrically driven and independently movable device according to the invention comprises a frame; at least three bearing wheels, at least one of which is turnably fastened to the frame; in connection with at least one wheel, there is provided a drive motor unit including an electric motor; a battery unit and an electric control unit, by intermediation of which the user controls and adjusts the operation of the device; a seat for the user of the device, which seat is arranged on top of the frame, and operation and control means, through which the user controls the operation of the device by intermediation of the control unit. According to the invention, the operation and control means are arranged in a control bracket fitted in connection with the seat.

It is an advantage of the invention that there are not needed any foot-operated drive and control devices, but all control operations are realized manually. It is another advantage that this arrangement simplifies the structure of the device.

In a preferred embodiment of the invention, the control bracket is connected at the side of the seat to form an arm-rest like structure. The advantage is that the control bracket is integrated effectively in the seat structures, so that the operation and control devices can be easily reached and operated by one hand.

In a preferred embodiment of the invention, at the side of the seat there is arranged a connecting element to which a control element can be detachable fastened. The

advantage is that the control element can be easily replaced by a new control unit, in case it is damaged or broken.

In a preferred embodiment of the invention, on both sides of the seat there are arranged essentially similar connecting elements to which a control element can be connected. The advantage is that the control bracket can be easily changed from one side of the seat to the other. Thus both left- and right-handed people can easily use the device.

In a preferred embodiment of the invention, the operation and control means comprise a control stick, a display device and preferably also a number of selection keys or the like. In a particularly advantageous embodiment, the operation and control means comprise a control stick and a touch-sensitive display unit, by which said display unit and selection keys or the like are mainly replaced. The advantage is the simplicity of the operation and control devices, as well as the program-wise modifiability, particularly as regards the touch-sensitive screen.

In a preferred embodiment of the invention, the display unit, particularly a touch- sensitive display unit, are attached to the control bracket so that their positions can be adjusted. The advantage is that both the viewing and manipulating angle of the display unit can be changed according to the conditions, so that the data and/or the selection keys arranged in the display unit are well visible and easily operated.

In a preferred embodiment of the invention, in the vicinity of the control stick, preferably at the free end thereof, there is arranged a selection switch by which the forward/rearward motional direction of the device can be selected. The advantage is that the controllability of the device is improved.

In a preferred embodiment of the invention, the seat and the control bracket there along are pivoted turnably in the horizontal direction to the top part of the frame. In the most advantageous embodiment, the slewing angle of the seat is at least 90 degrees, preferably within the range 90 - 270 degrees. The advantage is that a device provided with this kind of seat is easy and safe to move both forward and backward; the seat is simply turned for 180 degrees. Another advantage is that in the intermediate position of the seat, it is easy to climb in the device and to step down therefrom.

The control arrangement according to the invention for an independently movable device with electric drive; comprising a frame; a seat for the user of the device, said seat being arranged on top of the frame; at least three bearing wheels, at least one of

which is turnably attached to the frame; in connection with at least two adjacent wheels separate drive motor units provided with electric motors; and a battery unit; includes an electric control unit, by intermediation of which the user controls and adjusts the operation of the device, and operation and control means through which the user controls and adjusts the operation of the device by intermediation of the control unit. According to the invention, the operation and control means are arranged in a control bracket provided in connection with the seat, so that the user of the device, sitting on the seat, controls them, said operation and control means comprising a control stick, a display unit and a number of selection keys or the like; and the electric motor of each drive motor unit is realized as a servo motor, particularly and AC servo motor that is connected to the hub of the wheel, and where the control stick is used for adjusting the servo motors belonging to the drive motor units through intermediation of the control unit.

An advantage of the invention is the simplicity of the control arrangement. This is based on the servo motor, used in the drive motor unit, which is easily and effectively adjustable. Drive motor units are adjusted by means of an electric control unit that is realized preferably as a digitally programmed unit, such as a control unit based on logic circuits and/or a microprocessor. In that case, from the control unit there is for instance directly given an electric speed guideline value for one or several drive motor units, the outcome of which is observed directly from the measurement circuit of the servo motor feedback sensor. In an electric servo motor, particularly an AC servo motor, there is generally integrated the electric motor proper as well as its feedback sensor, such as a pulse sensor, a resolver or a tachometer. On the basis of the measurement data obtained from the feedback sensor, the angle position and rotation speed of the motor axis are known. It is pointed out that earlier electric servo motors are generally used for instance in industrial robots or similar applications, where the servo motors are used for adjusting for instance the position of swinging arms, such as their slewing angle or location.

It is a particular advantage of the invention that the electric servo motor also serves as a brake device when the motional speed of the device should be reduced and/or the device should be kept in place. The features of a servo motor, particularly an AC servo motor, include that with zero speed, the motor has a high torque, by which it keeps even a large load, in this case the device, in place. Also with low velocities the servo motor has a high torque, in which case the starting of the rotation of the drive motor units and hence the start-up of the device as well as the reaching and

maintaining of the desired guideline speed are carried out without unreasonably stressing the electric motors, even if the weight and load of the device were comparatively large.

An advantage of the invention is that the adjusting and control arrangements of the device can be optimized and modified depending for instance on the applications in question, such as the tasks of the device. By utilizing the adjusting features of the drive motor units, the efficiency and motional capacities of the device can be further optimized and improved. The rotary direction of the outlet axis of the drive motor units can be selected, and it can easily be changed. Thus the device can, by means of the drive motor units, be easily moved both backward and forward.

It is a particular advantage of the invention that all electric servo motors of the drive motor units can be adjusted and controlled separately for obtaining the desired motional speed and even orientation. The driving motors of the pair of wheels of the device can be controlled so that in the pair of wheels, the wheel driven by one drive motor unit rotates forwards in one direction, and the wheel driven by the other, parallel drive motor unit rotates backwards in the other direction. Thus the wheels in said pair of wheels rotate in different directions, in which case the device can be turned essentially on the same spot.

An advantage of the invention is that the anti-slip function for the wheels is realized by electric servo motors

An advantage of the invention is that owing to the electric servo motors employed in the motor units, the device has versatile driving features, and thus they remarkably improve the controllability of the device.

Another advantage of the invention is that the drive motor unit is quiet and pollution-free. The drive motor unit is electrically driven, and all moving, i.e. rotating parts are preferably arranged inside a uniform drive motor unit. Any exhaust gas emissions do not occur, as is the case with combustion motor driven machinery. Likewise, there is no danger of hydraulic fluids leaking to the ground, because the device does not include hydraulic cylinders or motors.

It is a particular advantage of the invention is that owing to the electric servo motor, the drive motor unit can be realized as a tight, compact structure. It is a particular advantage of the invention that the in a preferred embodiment, the drive motor unit is made as a uniform entity, such as a module that includes, apart from an electric servo motor, also a gear, particularly a reduction gear, such as a planetary gear or a

cogged gear. The advantage is that the rotation speed of the outlet axis can thus be dropped for instance to 1/5 - 1/30 of the rotation speed of the servo motor, and the wheel rotation speed can be adjusted to be suitable for the device. An advantage of the planetary gear is a higher efficiency in comparison with a cogged gear, in which case the total efficiency of the drive motor unit is further improved. The efficiency of the planetary gear can be even 95%.

It is an advantage of the invention that in comparison with corresponding known devices, such as lawn mowers, the weight of the device is made remarkably smaller. This also affects the power consumption of the device as well as the effective time of usage of the batteries, which is extended.

An advantage of the invention is that the center of gravity of the device is obtained near the ground surface. This is due to the fact that the drive motor units are mainly located in the bottom part of the frame and/or below the frame, and that the battery space is located in the frame, preferably on the level of the wheels.

An advantage of an AC servo motor is that it works with a high efficiency. Particularly with an AC servo motor, the efficiency rises even up to 95%. This is important, because the device is battery-driven, and thus the effective working time between the charging of the batteries is extended.

In a preferred embodiment of the invention, the device can be provided with detachable tools that are controlling by means of the operation and control means and the control unit. The advantage is that the device is thus arranged as a movable chassis where various tools can be installed, such as a lawn cutting unit, a cleaning brush and a snow plough, according to the needs of usage, and all of said tools are managed and controlled by operation and control means arranged in one and the same control bracket.

In a preferred embodiment of the invention, the device control unit can be provided with separate control modules or corresponding programmable units by which each installed and replaceable tool can be effectively used and controlled.

The invention and its further advantages are described in more detail below, with reference to the appended drawing where

Figure l is a perspective illustration of a light, electrically driven and independently movable device, particularly a device for cutting lawns,

Figure 2 is a top-view illustration of the device of Figure 1,

Figure 3 shows the device in partial cross-section B - B at the front wheels;

Figure 4 illustrates a partial cross-section C - C of the machine at the vertical axis of the rear wheel;

Figure 5 is a side-view illustration of the rear portion of the frame and the rear wheel with its fastening arrangements, seen in partial cross-section;

Figure 6 is a perspective top-view illustration of the seat and the control bracket connected thereto, seen at an inclined angle from the right;

Figure 7 is a top- view illustration of the seat and the control bracket;

Figure 8 is an exploded and enlarged illustration of how the control bracket and the connecting element are interconnected;

Figure 9 is a top-view illustration of a device with a turnable seat;

Figure 10 is a block diagram illustrating the control arrangements of the device, particularly as regards the controlling of the drive motor units, and

Figure 11 is a block diagram illustrating the control arrangements of the device, particularly as regards the tools.

Like numbers for like parts are used in the drawings.

A light, electrically driven device 1 according to the invention is illustrated in Figures 1 - 3. The device is mainly designed for maintenance, repair and/or cleaning tasks carried out mainly in yard areas or the like, but it is also suited in other corresponding light machinery tasks. In this case the device in question is device 1, in connection with which there are arranged means 2 for cutting lawn. The device 1 represents an example of light electric independently movable machinery.

The device 1 comprises a frame 4 provided with at least three wheels 3; 31, 32, 33. The frame 4 rests against the ground supported by the wheels 3. The device 1 is provided with a number of drive motor units 5 connected to the wheels for moving the device 1. The drive motor unit 5; 51, 52 is preferably arranged in connection with at least two wheels 3; 31, 32. Each drive motor unit 5 is provided with an electric motor 5a. The operation of the drive motor units 5; 51, 52 is adjusted by a device control unit 11. The device includes a battery unit 6 composed of a number

of electrically interconnected batteries and providing electric energy for running the drive motor units 5, for example.

The device includes a seat 7 for the 1 user of the device, arranged in the frame 4, particularly in the top part 44 of the frame. In the vicinity of the seat 7 and simultaneously in the vicinity of the user, there are arranged operation and control devices 9 for adjusting and maintaining the movements and functions of the device.

The frame 4 of the device 1 is preferably realized as a self-supporting structure. Now the frame 4 is in itself a rigid structure that keeps its shape without particular support structures. In its basic shape, the frame 4 is an elongate straight prism with a bottom and top part that are mainly rectangular (or modified therefrom), the side walls and ends of constituting a solid frame structure around the bottom part. Inside the frame 4, there is arranged a space that is divided between the different functional units and preferably separated into suitable sub-spaces by light and rigid division walls and/or lids or corresponding case structures. Now the control unit 11 is arranged in a case arranged in connection with the device frame, or in a similar protected control unit space 13 that can be locked. The batteries for storing electric energy are collected as a battery unit 6 that is respectively arranged in a battery space 12.

The frame 4 comprises the basic frame 41 proper, the front and rear portions 42, 43 permanently connected thereto, and a top part 44. In the direction of the lengthwise axis A - A of the frame, the basic frame 41 is an elongate basin-like space that is open at the top. The basic frame 41 is covered by the frame top part 44. The battery space 12 and the control unit space 13 are arranged in the interior of the basic frame

41. The pair of wheels 3; 31, 32 is connected to the front part 42 of the frame, on the opposite sides thereof, and they constitute the front wheels of the device.

The end portion of the frame, particularly the front part 42, is formed as a fork. This fork comprises two brackets or branches 42a, 42b provided as extensions of each long side of the frame 4, particularly of the basic frame 41, and the space left in between said brackets or branches forms a cavity 46 in the end of the frame. In the top part of the frame front portion 42, and simultaneously in between the branches 42a, 42b, there is arranged a plate-like lid element 42c. This is preferably realized as a perforated, plate-like element. By means of the lid element 42c, the branches 42a, 42b are interconnected, and at the same time the cavity 46 is covered.

In the front part of the frame 42, in this case in connection with the branches 42a, 42b, in the vicinity of the front edge of the lid element 42c, there also are arranged fastening elements 27 for the tools. By means of these, the tools used in the device, such as the cutting units 2a of the cutting device in Figures 1 and 2, are attached in place in the device at the support frame 2b.

The rear portion 43 of the frame is connected to the rear end 41b of the basic frame 41. In this embodiment, the rear portion 43 of the frame is made as a support structure for a third wheel 3; 33 i.e. a rear wheel. The rear wheel 33 is fastened to the rear wheel support 18 turnable with respect to the vertical axis D - D, so that the vertical axis passes through the rear wheel hub 3b (cf. Figure 5).

Instead of one rear wheel 33, a second pair of wheels is easily connectable to the frame and particularly to the rear end 41b of the basic frame 41 on its opposite sides near the frame rear portion 43, in which case they constitute the rear wheels of the device.

The frame 4 also comprises a top part 44 that is preferably at least partly detachable from the frame 4. The top part 44 is arranged to cover the basin-like basic frame 41 of the frame. The top part 44 extends from the front end 41a of the basic frame 41 to its rear end 41b. In structure, the top part 44 is a rigid, plate-like and essentially rectangular element.

In connection with the frame 4, advantageously on top of the top part 44, there is arranged a seat 7 for the user of the device. In the device according to the drawings, the lid element 42c is arranged to serve as a foot rest for the person sitting in on the seat 7 of the device.

The independently movable device with electric drive is provided with at least three bearing wheels 3; 31, 32, 33, of which one pair of wheels 31, 32 is located in the front part 42 of the device frame 4, on opposite sides thereof, and one wheel 33 is located at the opposite end of the frame in relation to this pair of wheels. As an alternative, the device includes four wheels 3, which are arranged in pairs at the front and rear ends of the device.

The drive motor unit 5; 51, 52 is arranged in connection with both wheels 31, 32 of the pair of wheels 3. The device user controls and adjusts the operation of the drive motor units 5; 51, 52 by means of the control unit 11, by using the operation and control devices 9 provided in the control bracket 8 of the device.

The drive motor unit 5; 51, 52 comprises an electric motor 5 a, the rotatable outlet axis of which is connected to the hub 3a of the wheel 3; 31, 32. In a preferred embodiment, the drive motor unit 5; 51, 52 includes, apart from the electric motor, also a gear 5b, particularly a reduction gear, for dropping the rotation speed of the electric motor to be suitable for the device. Now the rotatable outlet axis of the electric motor is connected to the inlet axis of the reduction gear, and its outlet axis further to the hub 3a of the wheel 3. Thus the drive motor unit 5 is realized as a solid, compact structure that can be provided in connection with the hub 3a of the wheel 3.

The electric motor 5a is realized as a servo motor, preferably an AC servo motor or as an alternative a DC servo motor. The desired guideline values, such as the speed guideline value, can be directly fed into the control unit 11 of the servo motor for adjusting said servo motor, and there can be directly obtained the position data of the servo motor (or if necessary) of the axis, as well as the rotation speed data to the electronic control unit 11. The AC servo motor is advantageously realized as a permanent magnet synchronous motor, the rotor of which is made of permanent magnets.

An advantage of an AC servo motor is that it works with a high efficiency, particularly within that power range that is well suited for the device according to the invention. Another advantage is that it is small in size, light in weight and economical in expenses. Yet another advantage is that its rotation speed is easily adjustable. Yet another advantage is its high torque at zero speed and immediately at the beginning of the rotary motion, as well as with low rotation speeds.

The drive motor unit 5; 51, 52 is formed as a module (cf. Figure 2), including a servo motor, particularly an AC servo motor 5a and a gear 5b, particularly a rotation speed reduction gear. This module is realized so that the AC servo motor 5a and the gear, particularly a planetary gear, 5b are mutually fitted with drive shafts coaxially in succession. However, it is pointed out that also other AC servo motor and gear combinations can be applied in the device according to the invention.

The rotatable outlet axis of the drive motor unit 5; 51, 52 is connected to the hub 3a of the wheel 3; 31, 32, as was explained above. The front wheels 31, 32 and their drive motor units 51, 52 are advantageously attached to the branches 42a, 42b of the front part. In length, the drive motor units 51, 52 are relatively short, which means that they do not remarkably narrow the available space between the branches 42a, 42b. The fastening elements for the drive motor units 5; 51, 52 are arranged in

connection with the frame, preferably the central part 41 thereof. The fastening elements are realized as an installation tube or sleeve 17; 171, 172. The wheel 3; 31, 32 is detachably fastened at the rim 3d to a rotatable power transmission axis, i.e. to the outlet axis 20 of the drive motor unit 5; 52, 52.

In the device according to figures 1 - 3, in the device frame 4, particularly in the frame rear portion 43, there is arranged a wheel that is turnable in relation to the vertical axis D - D, or as an alternative a turning wheel 3; 33. In case the rear wheel 3; 33 is realized as a turnable wheel, the device can be conducted in the desired direction when turning it. The wheel 3; 33 is connected, by intermediation of the wheel support 21, to the frame 4, particularly to the frame rear portion 43 (cf. Figures 4 and 5). The turning device 22 is connected to the wheel support, and thereby the wheel support together with the wheels can be turned, within the desired angle range, on both sides of the lengthwise axis A — A. As an alternative, the wheel 3; 33 is freely turnable in relation to the vertical axis, in which case the device is controlled by suitably driving the pair of wheels, i.e. in this case the front wheels 31, 33, for instance at different velocities.

The wheel support 21 is advantageously realized as an L-shaped element that is preferably bent of metal plate, such as steel plate. The first branch 211 of the wheel support 21 is attached to the rear portion 43, so that it is positioned essentially horizontally. In that case the second branch 212 of the wheel support 21 is directed downwards, essentially at an angle of 90 degrees with respect to the first branch 211. The installation tube 17; 173 is fitted in the aperture passing through the second branch 212 and supported against the branch. The drive motor unit 5; 53 is fitted in the installation tube 17; 173 in similar fashion as in the above described fastening arrangement of the drive motor units 5; 51, 52 of the pair of wheels. The rear wheel 3; 33 also is respectively fastened to the installation tube 17; 173 and in connection with the drive motor unit 5; 53.

The wheel support 21 is fastened by an axle stub 23 parallel to the vertical axis B - B and by connected vertical bearings 24 turnably at the first branch 211, underneath the rear portion 43, and in the middle region thereof. In this embodiment, the turning device 22 comprises a first and second idler wheel 221, 222, a cogged belt 223 (or a corresponding endless power transmission means, such as a belt or a chain) connecting their circumferences, and a slewing motor 225 (cf. Figures 4 and 5). The first idler wheel 221 is connected to the axle stub 23 and the second idler wheel 222 is connected on the same plane, at a distance from the first. The cogged belt 223 passes around both idler wheels 221, 222. In connection with

the cogged belt 223, it also is advantageous to use a belt tightener 224. The slewing motor 225 is arranged on the axis of the second idler wheel 222 and fastened to the frame 4; 41, 43. The slewing motor 225 is an electric motor, particularly a servo motor, such as an AC servo motor, the operation of which is controlled by the operation and control devices 9 arranged in the control bracket 8 of the device.

The rear wheel 3; 33 is realized as the wheel driving the device. Thus the device is realized as a vehicle with all- wheel drive. In that case the device has good features for traversing the ground. Another advantage is that the installation of the drive motor unit 5; 53 as such is stationary and similar to the other drive motor units 5; 51 , 52 provided in the device.

The seat 7 provided for the device user is arranged on top of the frame 4, particularly on top of the frame top part 44. The device control bracket 8 is arranged at the reach of the user in the vicinity of the seat 7, particularly in connection with said seat. The control bracket 8 comprises operation and control devices 9 for controlling the device and for adjusting the functions.

In a preferred embodiment of the invention, the control bracket 8 is attached at the side of the seat to form a structure resembling an arm rest. In that case the control bracket 8 can be attached to the seat 7 proper, for instance to its back rest 7b or bottom part 7a, or to the seat frame, for instance to its foot portion or the like. Most advantageously the control bracket 8 is arranged as an arm rest in the seat on either side of the seat, particularly of the seat bottom part.

The operation and control devices 9 for managing the functions of the tools connected to the machinery 1 and for controlling the functions thereof are arranged in the control bracket 8 (cf. Figure 8) within the reach of the user, in the vicinity of the seat 7.

The operation and control devices 9 comprise a control stick 9a or a similar control device, the position of which is mechanically adjustable, controlled by one hand, by which device 1 the motions and speed of the device are adjusted. The operation and control devices 9 also comprise a suitable display device 9b and a keypad and/or a number of selecting keys that are advantageously located in the immediate vicinity of the control stick 9a. All operation and control devices 9 are splash-proofed.

As an alternative, the display device 9b can be a touch-sensitive screen unit, in which case any separate keys, switches and/or selecting keys are necessarily not needed, or at least their number can be kept moderately small.

In a preferred embodiment of the invention, the display unit 9b is attached to the control bracket 8 so that its position can be adjusted. In that case the display unit 9b is fastened for instance by a shaft and a ball joint 10 to the control bracket 8, particularly in the vicinity of the free end thereof. The shaft is preferably a telescopic shaft with an adjustable length. The display unit 9b can be locked in place, in an adjusted position, and respectively it can be released by suitable locking elements. As an alternative, the fastening of the device can be realized by means of a suitable bendable shaft.

The control bracket 8 is arranged to extend essentially by 40 - 50 cm forwards from the back rest 7b of the seat 7, aside the seat bottom part. When the device user is sitting on the seat 7 with his back against the back rest, his hand extends to rest on the control bracket 8, and it particularly extends as far as the control stick 9a.

An advantage of the control bracket 8 and of the operation and control devices 9 installed therein is that they fit in a relatively small space and are thus easily arranged in connection with the seat 7.

In a preferred embodiment of the invention, in connection with the seat 7, preferably at the sides thereof, there is provided a connecting element 81 in which the control bracket 8 can be detachably connected. The control bracket 8 and the connecting element 81 are provided with mutually matching mechanical and electric connecting elements, so that the control bracket 8 can be easily detached and replaced. Through the connecting element 81, particularly through its electric connecting elements, the operation and control elements of the control bracket 8 are electrically connected to the control unit 11. Advantageously the electric connecting elements are connectors known as such and utilized in electronic devices.

In an embodiment, the mechanical connectors between the control bracket 8 and the connecting element 81 are realized for example by means of mutually matching ribs 811 and grooves 812. At the edges of the bottom surface of the control bracket 8, in the area (or part thereof) corresponding to the support surface of the connecting element 81, there are now provided ribs 811. At the opposite edges of the top of the connecting element 81, there are in turn arranged grooves 812, in which the ribs 811 can be fitted. Now the control bracket 8 can in the lengthwise direction be inserted by the ribs 811 to the grooves provided in the connecting element 81. In addition, in between the control bracket 8 and the connecting element 81, there are advantageously arranged locking means, such as a locking screw or the like, by

means of which said elements are immovably fastened to each other, and respectively by releasing said locking means, they can be mutually detached.

In another preferred embodiment of the invention, on both sides of the seat 7 there are arranged essentially similar connecting elements 81; 81a, 81b, to which the control device 8 can be connected. Now the position of the control bracket 8 can be changed from the right-hand side of the seat 7 to the left-hand side or vide versa. Thus both right- and left-handed users can drive and use the device.

In a third preferred embodiment of the invention, the length of the control bracket 8 is adjustable. In that case the control bracket 8 has a telescopic structure. It comprises two elongate mutually matched elements 8a, 8b, that are arranged so that one element can be slid inside the other, when the length of the control bracket 8 should be changed. The elements 8a, 8b of the control bracket 8 can advantageously be mutually locked to a desired length or respectively mutually released when adjusting the length.

The control bracket 8 can be provided with a suitable actuator, such as an electric motor, by which the change in length can be realized. Thus it can be realized for instance by keys/buttons belonging to the operation and control devices 9 and/or by means of a touch-sensitive screen 9b and a control unit 11.

In a preferred embodiment of the invention, the top surface 8c of the control bracket 8 is at least partly coarsened. The coarsening is arranged particularly in that area where the user's hand and arm rest while working the device, i.e. in the area between the control stick 9a and the front surface of the back rest. In that case the top surface 8c is provided with a coarsened surface, for instance a pimply surface, or it is provided with a separate glued-on coarse coating, such as a net or a cloth. Now the hand of the user sitting on the seat 7 rests on the coarsened surface of the control bracket 8 and cannot accidentally slide along the surface. This makes working safe and ergonomic.

In a preferred embodiment of the invention, the seat 7 is turnably fastened to the frame 4, particularly to the frame top part 44 (cf. Figures 3 and 7). The seat 7 is advantageously realized so that it is pivoted at the lower and middle regions of the seat bottom part 7a to the frame top part 44. Now the bottom part 7a of the seat 7 is provided with a vertical bearing arrangement 26 that allows the seat 7 to be turned around its vertical axis (in the direction of the arrow 70) on the horizontal plane in relation to the frame 4; 44. In addition, in connection with said vertical bearing,

there are provided lock and release elements 27, by means of which the seat 7 is locked in a given turning position and respectively released therefrom for turning.

The seat 7 is turnable with respect to the bearing axis and simultaneously the vertical axis, at least for the magnitude of the angle α = 90 degrees, preferably 180 degrees. In the first functional position of the device, the seat 7 is oriented directly forwards, i.e. in parallel with the frame lengthwise axis A - A towards the front part 42 of the frame and locked in this position. When the locking of the seat 7 is released, the seat 7 can be turned from the first functional position α = 90 degrees (either clockwise or counterclockwise) of the device to the rest position, in which case it opens directly to the side of the device (illustrated by dotted lines in Figure 7), and the seat can be locked in place. Now both rising from the seat as well as sitting down on it are performed easily. When the locking of the seat 7 again is released, it can be turned from the rest position either back to the first functional position or, as an alternative, in the opposite direction and to the second functional position, which is at an angle β = 180 degrees with respect to the first functional position and opens directly towards the frame rear portion 43, in which it can be locked.

The advantage of the above described embodiment of the invention is that the device can be used with various positions of the seat, at least in the first and second functional positions. This makes the possibilities to use the device all the more versatile, when also taking into account that the device can be completed with various tools that can be typically tools that are pushed and/or pulled.

It is also advantageous that the seat 7 is attached to the frame so that it can, for a short length in the direction of the lengthwise axis A - A of the frame, be moved in suitable rails or the like.

As was already pointed out above, a drive motor unit 5; 51, 52 is arranged in connection with at least one pair of wheels 3; 31, 32. The user of the device 1 controls and adjusts the operation of each drive motor unit 5; 51, 52, 53 by means of the control unit 11 , by the operation and control devices 9 provided in the control bracket 8. The control system is illustrated as a block diagram in Figure 6.

In the most advantageous embodiment of the invention, an essential part of the drive motor unit 5 is the AC servo motor 5a. The electric power required by the drive motor units 5 is obtained from the battery unit 6 arranged in connection with the device 1. The state of charge of the batteries in the battery unit is observed by a

battery surveillance unit 61 arranged in connection with the control unit 11. Said control arrangement includes means for measuring the battery voltage, means for setting and recording the voltage limit and alarm means as well as a program module or a corresponding arrangement for utilizing said means. The output voltage of the batteries is observed by measuring the voltage, and when the output voltage of the batteries has dropped below the permitted voltage limit, the control unit 11 gives an alarm that is advantageously displayed in the display unit 9b. After giving the alarm, the batteries of the battery unit 6 must be charged relatively quickly from a suitable source of electricity, such as the electric mains.

Preferably the battery unit 6 of the device is realized of lithium-ion batteries. These are batteries where the potential energy content per weight unit is clearly larger than with ordinary lead batteries. Another remarkable advantage is that the selection of lithium-ion batteries as the source of electricity for the device further reduces the weight of the device in comparison with a situation where ordinary lead batteries were used.

The output voltage obtained from the batteries of the battery unit 6 is direct voltage. This direct voltage can be for instance within the range 24 - 100 V, which can be raised, when necessary, to a higher level, for instance to 220 - 400V, by a suitable DC/DC converter 30. The direct voltage obtained from said converter is used for feeding, in each driving motor combination 5; 51, 52, 53, the servo controller 301 provided in connection with the AC servo motor 5a. It is pointed out that particularly in the intermediate circuit of the servo controller 301, direct voltage is converted to alternating voltage required by the AC servo motor 5a. The servo controller 301 is used for adjusting and controlling the AC servo motor 5a, through the control unit 11 by the operation and control devices 9, particularly the control stick 9a, on the basis of the obtained control messages. From each AC servo motor 5a, there is collected measurement data, such as the outlet axis rotation speed and torque, for realizing adjusting feedback based on one or several difference signals to said motor.

The control stick 9a is used for controlling each drive motor unit 5, preferably in the following manner. In connection with the control stick 9a, there is provided a stick position sensor, which is connected to the control unit 11 , which in turn is provided with a control element interpreter 91 for interpreting the positions of the control stick on the basis of the messages received from the position sensor. From the stick position sensor, there is obtained the information of the direction in which the stick is being turned, as well as of the stick slewing angle. The control element interpreter

91, i.e. the interpretation means of the position sensor, is in this case realized by a suitable program module and arranged in the control unit 11. On the basis of the received messages regarding the position of the control stick 9a, the control interpreter 91 defines the speed and motional orientation of the device desired by the user, and on the basis of said data, among others the rotation speeds of the drive motor units 5 are adjusted.

In a preferred embodiment of the invention, the position data of the control stick 9a is arranged to be interpreted as follows. The straight, vertical position of the control stick 9a is the basic position, where control events are not going on, and where the functions of the drive motor units 5 are preferably locked to be immobile and/or in a free state. The turning of the control stick 9a to an inclined position with respect to the vertical plane (to the right or to the left) is interpreted as a motional direction in which the user wishes to turn, when the control stick is observed directly from the top. The angle of the control stick, and particularly its magnitude with respect to the vertical direction, is interpreted as the desired proceeding speed in said direction. Consequently, when the control stick 9a is turned from the vertical position, i.e. from the central point, forwards/backwards/to the right/to the left, there is directly chosen the proceeding direction according to said position. Respectively, the length of the trajectory of the control stick 9a and thus the size of the slewing angle in turn define the proceeding speed in said chosen direction. There is necessarily no need for any separate brake, but the drive motor unit/units 5 can be used against the motional direction, which stops the device.

In an alternative embodiment of the invention, in the vicinity of the control stick 9a, preferably at the free end thereof, there is arranged a selection switch 9c, by means of which the motional direction of the device, either forward or backward, can be selected. In this embodiment, the position data of the control stick 9a is arranged to be interpreted as follows. The basic position of the control stick 9a is a state where the control stick 9a is turned on the vertical plane backwards at an angle that represents its extreme position. Now there are not any control functions going on, and the functions of the drive motor units 5 are preferably locked to be immobile. In the first position of the selection switch 9c, the device is defined to proceed directly forward, when the control stick 9a is turned on the vertical plane from the basic position forwards. The further the slewing angle of the control stick is extended, the faster the device moves forwards. In the second position of the selection switch 9c, the device is defined to proceed directly backwards, when the control stick 9a is turned on the vertical plane forwards from the basic position. The further the

slewing angle of the control stick is extended, the faster the device moves backwards. The control stick angle and particularly its size with respect to the basic position is interpreted as the desired proceeding speed in the motional direction selected by the selection switch 9c. Also in this embodiment, the turning of the control stick 9a to a position that is inclined with respect to the vertical plane, i.e. to the right or to the left, is interpreted as the desired motional direction indicating a turn, when the control stick is observed directly from the top. The selection switch 9c is preferably realized as a press switch, but a reverse switch may also be a possible alternative.

An advantage with the above described combination of a control stick and selection switch is that the trajectory (or angle) of the control switch can be extended to be double in comparison with an earlier described control stick application. Thus the usability of the device is improved, because the trajectory of the control stick is extended, and the manner in which the user manipulates the control stick need not be as sensitive as in the earlier applications.

It is pointed out that the electric servo motor also serves as a brake device, when the motional speed of the device should be decreased, and/or when the device should be kept in place. The features of a servo motor, particularly an AC servo motor, include that with zero speed, the motor has a high drag torque, by which it holds even a large load, in this case the device, in place.

When necessary, the orientation data of the controlled wheels, such as the rear wheel 3; 33, is displayed on the display unit 9b. The orientation data is obtained from the wheel position sensor arrangement provided in connection with the control unit 11. This includes a position sensor 310 connected to the control unit 11. As an alternative, the slewing motor 225, preferably realized as a servo motor, such as an AC servo motor, is employed as the position sensor. In that case the position data of the swiveling axis, obtained from the servo motor, is monitored by the control unit 11 , particularly by a wheel position interpreter 320 provided in connection with the control unit, and said data is used for defining the angle of the rear wheel 3; 33 in relation to the device lengthwise axis A - A. Said angle data is advantageously presented as a suitable graph or as numerical data on the screen 9b of the operation and control devices 9. The advantage is that the position of the directionally adjustable wheels, such as the rear wheel 3; 33, is known, and thus the motional direction of the device is known already at the start and can, when necessary, be immediately corrected in order to avoid hazards.

The drive motor unit 5 based on an AC servo motor is particularly well suited in a device according to the invention, because the required wheel specific power is of the order 1 - 3 kW. Another advantage is that the AC servo motor is small in size, light in weight and economical in expenses. In addition, the AC servo motor speed range is wide and the torque high at zero speed and with low rotation speeds.

Yet another advantage of the invention is that the drive motor units 5 are easily and effectively adjustable. Advantageously the drive motor units 5; 51, 52, 53 are adjusted by a control unit 11 that is realized as a digitally programmed unit, preferably a control unit based on a microprocessor. In that case the adjusting and control arrangements are optimized and modified for instance depending on the various applications, such as the tasks of the device. The rotational direction of the outlet axis of the drive motor units 5; 51, 52, 53 can be freely selected and easily changed. Owing to the drive motor units 5, the device has versatile driving features, which remarkably improves the controllability of the device. All drive motor units 5 can be separately adjusted and monitored for realizing a desired motional speed and even orientation.

In a preferred embodiment of the invention, in connection with the control unit 11 , there is arranged an anti-slip unit 92. Said anti-slip unit 92 comprises means for measuring the torque of the drive motor units 5 and means for setting and recording the torque limits as well as an anti-slip program module or a corresponding arrangement for utilizing the messages received from said means. The momentary torque of each drive motor unit 5 is observed, and when the torque suddenly drops under the permitted torque limit, the rotation speed of the drive motor unit is dropped rapidly step by step, until the torque returns to the normal level. In case the wheels are slipping, it also is possible to send an alarm from the control unit 11 , which alarm is advantageously displayed in the display unit 9b.

Another preferred embodiment of the invention makes use of the fact that the electric servo motors of the drive motor units can be adjusted and controlled separately. Thus the turning of the device essentially in place can be realized by a swivel unit 93 arranged in the control unit 11. By means of said swivel unit 93, the driving motors 5; 51, 52 of the pair of wheels 3; 31, 32 of the device can be controlled so that in a pair of wheels, the wheel 31 driven by one drive motor unit 51 rotates in one direction, for example forwards, and the wheel 32 driven by the other, parallel drive motor unit 52 rotates in the other direction, such as backwards. Thus the wheels in said pair of wheels 3; 31, 32 rotate in different directions, and the device can be turned essentially on the same spot. In order to realize the

function described above, the drive motor units are adjusted by control commands obtained from the operation and control devices 9, which commands are transmitted and interpreted in the control unit 11 to be in suitable form for the drive motor units, and particularly for the swivel unit 93. Now for example an instruction for turning the wheels at a relatively steep angle, given as a control command and surpassing the preset guideline value, makes the wheels of the pair of wheels in question rotate in different directions, and hence the device turns practically on the spot. In that case the turning radius of the device is minimal.

It is a particular advantage of the invention that the drive motor unit 5; 51, 52, 53 is a solid, compact structure that is arranged in connection with the hub 3 a, 3b of the wheel 3; 31, 32, 33. In the most preferred embodiment, the drive motor unit 5 includes, apart from an AC current electric motor 5a, also a gear 5b, particularly a reduction gear, preferably a planetary gear. By means of the reduction gear 5b, the rotation speed of the outlet axis of the drive motor unit 5 is dropped for instance to 1/25 of the rotation speed of the AC servo motor. In addition, the torque generated by the drive motor unit 5 is high immediately at the start. Thus the driving features of the device, particularly control features, are improved with respect to a drive motor unit provided with an AC servo motor only. It is pointed out that a fairly low traveling speed is required of the device; in working usage, and provided with means 2 suited for cutting lawn, it is of the order 5 km/h, and the transport speed of the device for instance from one work site to another is of the order 10 - 15 km/h. Also the total efficiency of the drive motor unit 5 is high, particularly when used in connection with a planetary gear.

In the above described embodiment of the invention (cf. Figure 1 and 2), in connection with the frame 4 there are arranged means 2 for cutting lawn. Said means 2 comprise a number of cutting units 2a for cutting lawn. Preferably said cutting units 2a are arranged adjacently, but they can also be arranged in an overlapping fashion or in succession, depending on the size of the device and of the number of the cutting units. The cutting units 2a are attached to the support frame 2b and thereby further detachably to the front part 42 of the frame 4.

According to the invention, the device 1 can advantageously be provided with various tools, such as said one or several lawn cutting unit 2a, a snow plough, a brush reel or a spiked reel. For this purpose, the front part 42 of the frame 4 is provided with a fastening device 27, such as a fastening frame 27a, in connection with which the tools provided with corresponding matching elements can be detachably fastened.

In connection with the fastening device 27 of the device, there is advantageously provided an lifting/lowering device 28 that can be controlled by the operation and control means 9 by intermediation of the control unit 11 (cf. Figure 11). By using a lifting/lowering key or the like, belonging to the operation and control means 9, which key or button can, when necessary, be arranged for instance on a touch- sensitive screen 9b, there is given a control command, such as a lifting command, for the control unit 11 , which in turn switches, by intermediation of a relay 29, the voltage, such as the battery voltage V, to the lifting/lowering device 28 for realizing the lifting operation. Respectively, by using the lifting/lowering key, said control command is cancelled, and by intermediation of the relay 29, an opposite voltage is switched to the lifting/lowering device 28 for realizing a lowering operation. Now for instance the lawn cutting units 2a used as tools can be lowered down to the working position for cutting the lawn, and respectively lifted up, when the device 1 is being driven for example to a lawn that requires cutting or away therefrom.

The tools 35, such as lawn cutting units 2a attached to the device 1, are managed by using the operation and control means 9 fitted in the control bracket 8 of the device through the control unit 11. For this purpose, in connection with the device 1 there are provided coupling means 34, such as a coupling box, for corresponding coupling means, such as a coupling plug, provided in the tool. Through the connecting means 34 electricity, such as a suitable voltage V, is fed in one or several electric motors of the tools 35. In addition, sensors or measurement devices in general provided in connection with the tools 35 for monitoring the tools are connected through coupling means to the control unit 11 of the device 1.

In addition, the device comprises a first data transmission unit 38a, through which the device control unit 11 and a tool 35 provided with a corresponding second data transmission unit 38b communicate as regards the state of the tool and the control and adjustment procedures thereof, according to the instructions given by the user through the operation and control means 9.

The tools 35 are advantageously provided with an electric identifier 36, which can be read on the control unit 11, when the tool 35 is detected to have been connected to the device connecting means 34. In the memory of the control unit 11, there is recorded a list 360 of the tools to be used in connection with the device 1 and of their identifiers 36. On the basis of the list 360, a tool 35 attached to the device can be identified by a tool-specific electric identifier 36 connected thereto.

A tool-specific operation program 37 or a corresponding separate control module can be recorded as a maintenance procedure in the memory of the control unit 11, or it can be arranged in connection with the control unit. Thereafter the operation program 37 can be selected and activated by the display unit and the keypad/selection buttons of the operation and control means 9 from the memory of the control unit 11. As an alternative, the operation program 37 is implemented automatically, when a tool 35 is connected to the device and identified on the basis of the identifier 36.

The invention is not restricted to the above described embodiment only, but many modifications are possible within the scope of the inventive idea defined in the appended claims.