[DESCRIPTION] [TITLE] A Device and A Method for Driving An Elevator Door (TECHNICAL FILED1 The present invention relates to a device and a method for driving an elevator door. More particularly, the present invention relates to a device and a method for driving an elevator door which is installed to be opened and closed automatically on an elevator.

[BACKGROUNDART] In general, an elevator includes an elevator car and a pair of doors at a landing site on each floor. A door driving device for driving the doors is installed at a predetermined portion of the elevator car. When the elevator car arrives at the landing site of each floor, a pair of doors of the elevator car and the pair of doors of the landing site are engaged with each other and opened or closed by the door driving device installed in the elevator car. An elevator door system is defined to be devices including the door driving device as described hereinafter and other mechanical or electrical elements for opening or closing the door.

Referring to Fig. 1, an example of a widely known door driving device of an elevator is described. Fig. 1 shows a schematic block diagram of a conventional elevator door system and a conventional door driving device

included in the system.

As shown in Fig. 1, the conventional elevator door system 1 includes a door driving device 100 for controlling doors 30a or 30b to be placed at a predetermined position with electric powers supplied from a power source 10, pulleys 16a and 16b and an arm 18 for transferring torques provided from the door driving device 100 to the doors 30a or 30b, and at least two limit switches 20a and 20b turned on or off according to the position of the doors 30a or 30b.

In addition, the door driving device 100 of the conventional elevator door system 1 includes a motor 14 for providing torques and a motor controller 12 for driving the motor 14 in response to outputted signals from the limit switches 20a and 20b. Examples of the motor 14 used for the conventional door driving device 100 may includes a DC motor, a one-phase induction motor, a three- phase induction motor, etc.

Control characteristics for driving an elevator door, as described above, include ; 1) to drive the doors repeatedly moving within a predetermined distance, 2) in control of door opening or closing velocity and door position, 2-1) that it is not required to achieve a very precise position control of a so-called"servo-level control", in other words, that it is allowable to have position control tolerance of several millimeters.

2-2) that sudden accelerating or decelerating operation should

be prevented while the door is opened or closed.

According to the conventional door driving device 100 used in the conventional elevator door system 1, since driving operation of the motor 14 is totally dependent on on or off state of the limit switches 20a or 20b, there is a problem that smooth driving is difficult to open or close the door.

Further, in case additional parts are attached to compensate control precision, it causes problems of increase of cost, energy consumption, number of control elements, difficulty in control stability, etc.

[DISCLOSURE OF INVENTION] The present invention is suggested in order to fix the aforementioned problems, and the object of the present invention is providing a device and a method for driving an elevator door appropriate and stable to satisfy control characteristics of an elevator door. lDETAILED DESCRIPTION] In order to accomplish the object, the present invention provides a door driving device, which includes a power source for supplying electric power, a door moving a predetermined driving distance reciprocally, and a power transferring unit for transforming rotating motion into linear motion in order to open or close the door, including : a brushless DC motor for providing torque for driving the door and outputting a rotor's position signal (pr); and a controller for

determining operation state of the door on the basis of the rotor's position signal outputted from the brushless DC motor and driving the brushless DC motor in response to the determined operation state of the door.

Further, the present invention also provides a door driving method of an elevator door system, which includes a power source for supplying electric power, a door moving a predetermined driving distance reciprocally, a brushless DC motor for providing torque for driving the door and outputting a rotor's position signal (Pr) and a power transferring unit for transferring torque of the brushless DC motor to the door, the method including steps of: receiving a door driving command from a controlling device of the elevator system; receiving the rotor's position signal (pr) outputted from the brushless DC motor; determining operation state of the door on the basis of the received rotor's position signal (pr) ; and driving the brushless DC motor on the basis of the determined operation state of the door.

[BRIEF DESCRIPTION OF DRAWINGS] Fig. 1 shows a schematic block diagram of a conventional elevator door system and a conventional door driving device included in the system.

Fig. 2 shows a block diagram of an embodiment of an elevator door driving device according to the present invention and an elevator door system including the elevator door driving device.

Fig. 3a shows examples of waveforms of position signals of a rotor in

the brushless DC motor provided in the door driving device shown in Fig. 2.

Fig. 3b shows a data table of binary-codes of waveforms shown in Fig.

3a.

Fig. 4 is a flow chart showing operation processes of the door driving device shown in Fig. 2 according to an embodiment of the present invention.

Fig. 5 shows a functional block diagram of a controller used for the door driving device shown in Fig. 2.

Fig. 6 shows a schematic block diagram of an elevator door driving device according to another embodiment of the present invention.

*Explanation of symbols of some parts in the drawing 1,2 : an elevator door system 10: a power source 30a, 30b: doors 1 00a, 1 00b, 200: a door driving device 16,18 : a power transferring unit [BEST MODE FOR CARRYING OUT THE INVENTION] In the following, preferred embodiments of the present invention are described in detail with reference to attached drawings.

Referring to Fig. 2, Fig. 2 shows a block diagram of an embodiment of the elevator door driving device according to the present invention and a elevator door system including the elevator door driving device. As shown in Fig.

2, the elevator door system 2 including the door driving device 200 of the present invention includes a power source 10 for supplying electric power, a pair

of doors 30a and 30b which are opened or closed by moving reciprocally in a predetermined moving distance, a door driving device 200 for driving the doors 30a and 30b by using supplied power from the power source 10, and a power transferring unit, namely pulley 16 and arm 18, for transferring torque from the door driving device 200 to the doors 30a and 30b.

Details, modifications, and applications of the power source 10, the doors 30a and 30b, and the power transferring unit 16 and 18 are already widely known in the art, and thus may be omitted.

The door driving device 200 of the present invention especially includes a brushless DC motor 214 for providing torque to drive the doors 30a and 30b and outputting position signal (pr) of a rotor thereof. Characteristics and usages of the rotor's position signa ! (pr) produced by the brushless DC motor 214 will be described in more detail, later.

Further, the door driving device 200 determines operation state of the doors 30a and/or 30b on the basis of the rotor's position signal (Pr) outputted from the brushless DC motor 214, and includes a controller 212 for driving the brushless DC motor 214 on the basis of the operation state of the doors 30a and/or 30b.

Now, an examplary embodiment of the rotor's position signal (Pr) provided by the brushless DC motor 214, which is widely known at the present time, is described in detail. Fig. 3a shows waveforms of the rotor's position signals (Pr) of a three-phase brushless DC motor 214 included in the door

driving device 200 shown in Fig. 2. Fig. 3b shows a data table formed by binary- coding the waveforms shown in Fig. 3a.

The three-phase brushless DC motor 214 includes three Hall sensors, one of which is representatively designated by 216 in Fig. 2, installed at intervals of 120 degrees of electric angle in order to be corresponded to predetermined positions of a stator thereof, so that each of the Hall sensors 216 detects a rotor's position and outputs the rotor's position signal (p,) as shown in Fig. 3a.

The controller 212 drives the three-phase brushless DC motor 214 by using the rotor's position signals (pr) according to a predetermined rule. Each of the rotor's position signals (pr), as shown in Fig. 3a, has high and low outputs alternately at every 180-degree in the electrical angle (8), and there are three kinds of position signals having phase differences of 120 degrees among one another.

Therefore, it is possible to acquire an identifiable output at every 60-degree in the electrical angle by using the rotor's position signal (pr).

Fig. 3b shows a data table acquired by binary-coding the outputted position signal of each phase by mapping a high output to"1"and a low output to"0"with 60-degree in the electrical angle as a unit. As shown, considering the data acquired from A, B and C phase position signals as 3-unit binary coded data, the rotor's position signals (pr) provided by the 3-phase brushless DC motor are in the format of gray codes.

Therefore, since outputs are identifiable at every 60-degree in the electrical angle, a possible maximum error in position control is equal to or less

than 60 degrees in the electrical angle, and is equal to or less than 120 degrees per number of poles in mechanical angle domain. In general, a small brushless DC motor adopts 4,6 or 8 poles, and the mechanical possible maximum error may be 30,20 or 15 degrees, respectively, in case of the conventional small brushless DC motor.

In order for a better understanding, this maximum possible error, or resolution, can be converted into distance by using the equation of {(circumference of motor shaft)/ (a constantxnumber of poles)}, thereby the maximum possible errors in distance are 2.5, 1.67 and 1.25 millimeters, respectively, in case of motors having 4,6 and 8 poles with shafts of circumferences of 30 millimeters. In this way, it is possible to achieve a sufficient level of precision to control positions of the elevator doors.

Further, in case the rotor rotates in an opposite direction to the case described above, order of signals outputted in each phase is opposite to that in the above described case so that rotating direction of the motor 214 can be detected by using this fact.

Of course, type or size, etc. of the brushless DC motor 214 is not limited if it is appropriate to be used for the door driving device 200 of the present invention. On the other hand, the most effective method for using the 3-phase brushless DC motor has been explained in the above, but it should be understood that a method for using a rotor's position signal (pr) of a brushless DC motor is not limited to that described above. For instance, it may also be

used to detect rotating direction based on signals of two phases and velocity based on signals of the other phase, or to detect both velocity and rotating direction based on signals of only two phases, etc.

The door driving device 200 of the present invention performs following operations using the rotor's position signal (pr) produced by the brushless DC motor 214 having the waveform as described above. Hereinafter, there will be described an embodiment of a method for using the rotor's position signa ! (pr) of the 3-phase brushless DC motor 214. if the rotor's position signa ! (pr) of waveforms as described above is used, operations performed by the end-limit switch of the conventional elevator can be embodied as a software program, and thus the doors 30a and 30b can be driven precisely and easily without an extra hardware like the end-limit switch.

In order to embody this, the door driving device 200 of the present invention performs an operation for measuring a door driving distance when it is first installed, an operation for outputting an end-limit signal and an operation for initializing at power-on, etc. Detailed description will follow.

First of all, the operation for measuring a door driving distance at installation is to measure a distance (defined as"a driving distance"in the present specification) from a location where the doors 30a and 30b are fully opened to a location where the doors 30a and 30b are tightly closed.

That is to say, the elevator doors 30a and 30b are driven to be fully opened (or tightly closed) at the first installation, then a moving distance of each

of the doors 30a and 30b is measured until each of the doors 30a and 30b is tightly closed (or fully opened), namely the door 30a or 30b does not move any further, in the opposite direction at a low speed from the above locations as starting points.

Next, this moving distance of each of the doors 30a and 30b is stored in the controller 212 as a driving distance of the doors 30a and 30b to which the door driving device 200 is installed. Herein, in order to minimize an error which <BR> <BR> may be caused by belt slip, etc. , it is preferred that the doors 30a and 30b are driven at as slow speed as possible.

Calculation (or measurement) of the moving distance may be performed by multiplying the number of the rotor's position signals (pr), which are inputted during the first driving of the doors 30a and 30b, to the resolution of the brushless DC motor 214, and determined by the following equation. That is to say, [Equation 1] a moving distance = (number of the rotor's position signals) x [ (circumference of shaft) / (number of poles x number of phases)] Of course, the method for calculating the moving distance may be changed according to selection of rotor's position signals (pr). But, the new method is not quite different from the case of the Equation 1, and the selection is just one of design options in embodiments, thus detailed description about them is omitted.

By setting door driving patterns, such as a maximum velocity, accelerating or decelerating time after the driving distance is measured as described above, a moving distance of the door 30a or 30b, which means present location of the door 30a or 30b, can be known and velocity of the door 30a or 30b can be calculated from the moving distance and time of the door 30a and 30b. Therefore, the doors 30a and 30b can be driven smoothly by controlling the rotating velocity of the motor 214 precisely without any extra velocity detector.

In order to drive the elevator system safely, in general, the controller of the elevator system is designed to receive end-point signals indicating that the door 30a or 30b reaches a predetermined stop position.

In the conventional elevator door system 1, output of the end-limit switch out of the limit switches 20a and 20b is transmitted directly to the controller of the elevator system as an end-point signal. But, the limit switches 20a and 20b produce signals by physically contacting the doors 30a and 30b, and thus there are problems like malfunction, breakdown, etc. mainly resulted from being deteriorated by long use.

On the contrary, the door driving device 200 of the present invention removes the needs for using the conventional end-limit switches by performing the end-point signal outputting operation as described hereinafter. That is to say, in case the doors 30a and 30b are determined to be in the state where they are fully opened or tightly closed, the door driving device 200 produces the end-

point signal by itself and transmits the produced signal to the controller (not shown) of the elevator system.

A method for determining whether or not the door is in the fully opened state (or the tightly closed state) is, for example, that the moving distance of the doors 30a or 30b is calculated in real-time, and doors 30a and 30b are determined to be in its fully opened state (or the tightly closed state) when calculated moving distance is equal to the driving distance. In case the above described method is used, an error may be occurred due to, for example, belt slip, etc. Therefore, the method may be modified to determine whether or not the door 30a or 30b is in its fully opened state (or the tightly closed state) when output of the rotor's position signal (Pr) does not change for a predetermined time.

As described above, according to the end-point signal outputting operation of the door driving device 200 of the present invention, an extra hardware like the end-limit switch is not required, thereby the installation of the door driving device 200 is much easier than the conventional case, and it is possible to remove or decrease the possibility of malfunction or breakdown caused by mechanical friction or deterioration.

Finally, the initialization driving operation at the time of power-on is described in detail. This operation is to move the doors 30a and 30b to an initial location which can be a temporary reference point, because there might not be information on a present location of the doors 30a and 30b at the time of power-

on of the door driving device 200. The initial location can be the above described fully opened state or the tightly closed state of the doors 30a and 30b. That is to say, the door driving device 200 drives the doors 30a and 30b in the closing (or opening) direction, and the doors 30a and 30b are determined to be in its fully opened state (or the tightly closed state) if the rotor's position signal (Pr) does not change for a predetermined time, then the end-point signal is produced and transmitted to the controller (not shown) of the elevator system. By this, it is possible to acquire information on the present position of the doors 30a and 30b.

Now, referring to Fig. 4, the door driving operation, which is performed by the controller 212 included in the door driving device 200 in order to open or close the doors 30a and 30b after the initial installing operation including the driving distance measuring operation, etc. are completed and a power for ordinary driving is applied, is described in detail. Fig. 4 is a flow chart showing operation processes of the door driving device 200 shown in Fig. 2 according to an embodiment of the present invention.

First of all, if the power source is applied to the elevator door system 2 (step 400), the door driving device 200 performs the initializing operation (step 402).

Next, after the initializing operation is performed, the door driving device 200 enters a stand-by state (step 404), and waits for a door opening or closing command (hereinafter, collectively called as"door driving command") from the controller (not shown) of the elevator system.

Then, it is determined whether or not the door driving command is provided (step 406). As described above, the door driving command is either one of the door opening or closing command. In case any door driving command is not provided, the door driving device 200 remains in the stand-by state.

Next, in case a door driving command is provided, the brushless DC motor is driven according to type of the provided door driving command (step 408). The door opening or closing command can be interpreted as a command to rotate in the right or left direction for the brushless DC motor 214. Therefore, the brushless DC motor 214 is driven according to a predetermined operation rule by determining a rotating direction with type of determined command and analyzing the rotor's position signal (Pr).

Next, if the brushless DC motor 214 starts to rotate, the number of the rotor's position signals (Pr) inputted from the brushless DC motor 214 to the driving device 200 is counted (step 410). Herein, it is preferred that unit of the rotor's position signals (pr) counted is 3-bit binary-code generated by binary- coding outputs of each phase at every 60-degree in electrical angle, as shown in Fig. 3b. As described above, however, outputs from only one phase may be used according to practical applications and, in this case, counting inputted signal may be performed so that one signal gets inputted whenever the output voltage level is changed from high to low or low to high.

Next, for instance, moving distance of the doors 30a and 30b are calculated by using the Equation 1 according to counted number of the rotor's

position signals (pr) (step 412).

Next, if the calculated distance becomes equal to the driving distance stored in advance, it is determined that the doors 30a and 30b reach the stop position (step 414) and operation stops (step 416).

In general, the door driving device 200 performs its operations by receiving the door opening or closing command from the controller (not shown) of the elevator system but, according to applications, in case an input is provided from, for example, an opening button, a hall button, a door safety bar, etc. , the door driving device 200 should process this input by itself. Those skilled in the art can embody this process easily, and thus detail is omitted.

As a result of determination in step 414, if it is determined that the doors 30a and 30b does not yet reach the stop position, or the fully opened or tightly closed state, the door driving device 200 continues to drive the brushless DC motor 214 by returning its control to the step 408, and repeats steps 410 to 414.

Next, with reference to a functional block diagram shown in Fig. 5, the controller 212 of the door driving device 200 according to an embodiment of the present invention is described in detail. Preferably, the controller 212 included in the door driving device 200 of the present invention is embodied by programming a widely known micro-processor (not shown) and combining it with an appropriate hardware like a widely known driver circuitry (not shown) for the brushless DC motor. Fig. 5 shows an examplary functional block diagram including functional blocks performed by the programmed microprocessor and

other hardware. There can be various combinations of functional blocks according to practical design options.

As shown in Fig. 5, the controller 212 according to the present invention includes a door driving command operating unit 402 for receiving the door opening command to open the doors 30a and 30b or the door closing command to close the doors 30a and 30b and storing it temporarily, a door operating state processing unit 404 for receiving the rotor's position signal (pr) from the brushless DC motor 214 and determining operation state of the doors 30a and 30b by analyzing received rotor's position signal (Pr), and a motor driving unit 406 for driving the brushless DC motor 214 on the basis of the door opening or closing command received from the door driving command operating unit 402 and the doors'operation state determined by the door operation state processing unit 404. The door driving command operating unit 402 receives the door opening or closing command produced by a door open button, a door close button, a hall button, a door safety bar, etc. installed in the elevator door system 2. And, the door driving command operating unit 402 stores it temporarily and transmits it to the motor driving unit 406.

The door operating state processing unit 404 stores all of constants and <BR> <BR> variables, such as the driving distance, etc. , necessary to drive the doors, and calculates the moving distance and velocity of the doors 30a or 30b by analyzing the rotor's position signal (Pr) produced from the brushless DC motor 214.

Further, it is determined on the basis of theses constants and variables whether

or not the doors 30a and 30b reach the stop position. And, the end-point signal is produced as a result of the determination.

The motor driving unit 406 controls rotation, rotating direction, rotating velocity, etc. of the brushless DC motor 214 on the basis of commands and/or analyzed data provided by the door operating state processing unit 404.

Next, referring to Fig. 6, Fig. 6 shows a schematic block diagram of another embodiment of the elevator door system 2 to which the door driving device 200 of the present invention is applied. As shown in Fig. 6, the elevator door system 2 is configured to improve control precision of the door driving device 200 according to the present invention by using two-stage pulleys 16a and 16b for transferring torque from the brushless DC motor 214 to the doors 30a and 30b.

According to the present embodiment, control precision of the door driving device 200 according to the present invention increases proportionally to the ratio of shaft diameter of the second pulley 16b to that of the first pulley 16a.

[INDUSTRIALAPPLICABILITYI According to the present invention, it is possible to provide a device and a method for driving an elevator door, which can meet control characteristics of the elevator door, by utilizing the rotor's position signal (Pr) of the brushless DC motor 200 directly.

In addition, according to the present invention, it is also possible to

provide a device and a method for driving an elevator door driving device which not only performs necessary and sufficient control ability to satisfy control characteristics for the elevator doors, but also improves effectiveness of power consumption and control stability.