Title

Method and device for operating vehicle, and computer program product Technical field

The present invention relates to a method for operating a vehicle, a device for operating a vehicle, and a computer program product.

Background art

As automated driving technology and smart perception technology develop, more and more vehicles are being equipped with active suspension systems capable of reacting to current road conditions. However, most existing suspension control schemes rely on real time monitoring of road conditions, and therefore need to establish a completely new shock absorption model according to current road conditions for each occasion of travel, in order to plan suspension behaviour.

At present, a method for detecting the state of a road surface has been proposed in the prior art; in that method, based on a detected road surface state, a corresponding road surface type and travel parameters of a test operating stage are obtained from a memory, and these travel parameters are applied to an active suspension system to enable rapid execution of suspension control in response to road surface conditions when a vehicle is travelling.

A method for planning a vehicle path has also been proposed in the prior art, wherein road surface information is searched along a path of vehicle travel, road conditions are analysed with the aid of a processor (e.g. potholes or obstacles, etc. on a road surface) and combined in real time with a parameter configuration and travelling state of the vehicle itself, and multiple alternative path trajectories that avoid unevenness in the road are thereby calculated.

However, these solutions still have many shortcomings. In particular, the solutions currently proposed are only able to achieve rough differentiation of types of road surface travelled by vehicles, being unable to take into account road surface information in combination with geographical position, and also being unable to take into account maintenance and renewal of the road surface state. Furthermore, when ideal parameters contained in a general-purpose scheme are applied directly to a vehicle suspension system, personalized vehicle configurations are often ignored, and as a result it is not possible to guarantee that the ideal adjustment parameters called are favourably adapted to current vehicle driving behaviour.

Summary of the invention

An objective of the present invention is to provide a method for operating a vehicle, a device for operating a vehicle, and a computer program product, in order to solve at least some of the problems in the prior art.

According to a first aspect of the present invention, a method for operating a vehicle is provided, the method comprising the following steps:

51) acquiring road surface information of a route to be travelled by the vehicle and state information of the vehicle;

52) comparing the acquired road surface information with historical road surface data, and requesting an adjustment strategy for enabling the vehicle to provide passenger comfort on the route to be travelled according to a result of the comparison;

53) optimizing the adjustment strategy on the basis of the state information of the vehicle, such that the optimized adjustment strategy is matched to a current state of the vehicle; and

54) operating the vehicle according to the optimized adjustment strategy.

The present invention in particular comprises the following technical concept: the present invention makes it possible to use vehicle state information as an additional influencing factor to further optimize model quality when an initial framework of a passenger comfort model is established on the basis of empirical information, thereby advantageously transforming a conventional solution into an individual customized scheme, and ensuring that the individual needs of the vehicle are satisfied while reducing the cost of calculation. Thus, the overall operating characteristics of the vehicle are matched not only to the state of the road surface to be travelled but also to the vehicle’s current configuration and/or load state, thus further improving passenger comfort.

Optionally, the adjustment strategy requested in step S2 comprises a first adjustment mode and a second adjustment mode which can be implemented interchangeably, the first adjustment mode being implemented when the acquired road surface information is in agreement with the historical road surface data and in particular when the degree of agreement between the acquired road surface information and the historical road surface data satisfies a predefined condition, and the second adjustment mode being implemented when the acquired road surface information is not in agreement with the historical road surface data and in particular when the degree of agreement between the acquired road surface information and the historical road surface data does not satisfy a predefined condition, the second adjustment mode being different from the first adjustment mode.

The following technical advantages in particular are thereby realized: by checking the degree of agreement between the road surface information and the historical road surface data, it is possible to quickly deduce whether a known solution that can be directly called already exists in a historical database; this process saves a large amount of computing power, while increasing the efficiency of the scheme as a whole. In addition, by suitably selecting a threshold for the degree of agreement, changes in the road surface state (for example caused by weather, road maintenance or other reasons) are advantageously taken into account, while flexible adjustability of the desired comfort level is ensured. For example, compared with a vehicle operating scheme which assigns the highest priority to passenger comfort, the predefined threshold can be set lower when vehicle energy consumption is insufficient or some functions have failed. Optionally, in the first adjustment mode, a shock absorption characteristic of the vehicle is adjusted according to a pre-stored dynamical parameter, and in the second adjustment mode, a dynamical parameter of the vehicle is calculated in real time, and a shock absorption characteristic of the vehicle is adjusted dynamically according to the dynamical parameter calculated in real time.

The following technical advantages in particular are thereby realized: by defining adjustment modes that can be freely interchanged, the most appropriate adjustment strategy can be selected in real time according to the degree of matching with historical road surface data, thereby minimizing the cost of calculation used to providing passenger comfort.

Optionally, the adjustment strategy determined in step S2 comprises: dynamically adjusting a parameter setting of an active suspension apparatus of the vehicle; dynamically adjusting a torque vector distribution of a distributed wheel hub driving apparatus, such that motion of each wheel of the vehicle is independently controlled; and/or selecting a finely adjusted trajectory that reduces local road surface jolting along the route to be travelled.

Optionally, in step S3, an active suspension apparatus and a seat shock absorption apparatus of the vehicle are adjusted in a coupled manner according to the state information of the vehicle, wherein shock absorption amounts are distributed to the active suspension apparatus and seat shock absorption apparatus in particular according to load information and a centre-of-mass distribution of the vehicle, in order to reach a state that is optimal overall.

The following technical advantages in particular are thereby realized: especially in the case of a road surface with a lot of jolting, two cooperating shock absorption apparatuses are advantageous. This is because, in addition to impact forces exerted on the vehicle body by the uneven road surface being cushioned overall with the aid of the active suspension apparatus, fine adjustment of the shock absorption effect is achieved in a more targeted manner at the same time by means of the seat shock absorption apparatus. Thus, taking the state information into account, the shock absorption system is adjusted in two ways in a linked fashion, and this can significantly improve the comfort of passengers. Optionally, the state information of the vehicle comprises passenger weight information, passenger distribution information, passenger posture information and passenger physical condition information of the vehicle, in particular acquired at fixed time intervals.

The following technical advantages in particular are thereby realized: by acquiring passenger state information of the vehicle, it is possible to advantageously enable vehicle passengers to experience shock absorption characteristics corresponding to their current state, thereby further improving passenger comfort. Additionally, by acquiring this state information multiple times at time intervals, it is further possible to adapt a shock absorption strategy dynamically to changes in passenger state, thus increasing the reliability of the scheme as a whole.

Optionally, in step S3, an optimized adjustment strategy is determined independently for each seat of the vehicle. It is thereby possible to improve the comfort experience in a more personalized way in different regions of the vehicle, and in particular, not enable shock absorption measures in regions where there are no passengers, in order to provide an efficient and energy-saving scheme.

Optionally, in the second adjustment mode, the acquired road surface information and a corresponding adjustment strategy are updated to a historical database, in which historical database the historical road surface data is stored.

The following technical advantages are thereby realized: this data sharing mode makes it possible not only to add road surface information for each road section in the historical database, but also to replace obsolete data according to the latest road surface situation, in order to ensure that the solutions in the historical database are up to date.

Optionally, the historical road surface data is collected by at least one other vehicle by crowdsourcing and/or collected by the vehicle itself at a previous time and stored in a local and/or cloud-based historical database of the vehicle. The following technical advantages are thereby realized: with the aid of crowdsourcing data collection and a Big Data sharing model, it is possible to efficiently build a historical database within a short time, without the need to spend a huge amount of money on road mapping for the purpose of road surface inspection. By collecting data of road surfaces previously travelled by the vehicle itself, it is possible to store solutions for passenger comfort in a more focussed way for a specific driver’s driving preferences and usual driving routes.

Optionally, the method further comprises the following step: planning the route to be travelled by the vehicle on the basis of historical road surface data, wherein a route that reduces road surface jolting is automatically selected as the route to be travelled from at least one alternative route.

The following technical advantages in particular are thereby realized: when planning a route, the present invention in particular also takes into account in advance road surface information of the route to be travelled, and it is thereby possible in particular to control passenger comfort along the entire route overall, and select a route more suited to user needs on this basis.

According to a second aspect of the present invention, a product for operating a vehicle is provided, the device being used to perform the method according to the first aspect of the present invention, and the device comprising: an acquisition module, configured to be able to acquire road surface information of a route to be travelled by a vehicle and state information of the vehicle; a control module, configured to compare the acquired road surface information with historical road surface data, and request an adjustment strategy for enabling the vehicle to provide passenger comfort on the route to be travelled according to a result of the comparison; an optimization module, configured to be able to optimize the adjustment strategy on the basis of the state information of the vehicle, such that the optimized adjustment strategy is matched to a current state of the vehicle; and an execution module, configured to be able to operate the vehicle according to the optimized adjustment strategy.

According to a third aspect of the present invention, a computer program product is provided, wherein the computer program product comprises a computer program, the computer program being configured to perform the method according to the first aspect of the present invention when executed by a computer.

Brief description of the drawings

The present invention is described in greater detail below with reference to the drawings, to enable a better understanding of the principles, characteristics and advantages of the present invention. The drawings include:

Fig. 1 shows a flow chart of the method for operating a vehicle according to an exemplary embodiment of the present invention.

Fig. 2 shows a flow chart of one method step of the method for operating a vehicle according to an exemplary embodiment of the present invention.

Fig. 3 shows a block diagram of an exemplary vehicle comprising the device for operating a vehicle according to the present invention.

Fig. 4 shows a schematic drawing of the method according to the present invention being used in an exemplary application scenario.

Fig. 5 shows a schematic drawing of the method according to the present invention being used in another exemplary application scenario.

Detailed description of embodiments

To clarify the technical problem to be solved by the present invention, as well as the technical solution and beneficial technical effects thereof, the present invention is explained in further detail below with reference to the drawings and multiple exemplary embodiments. It should be understood that the particular embodiments described here are merely used to explain the present invention, not to define the scope of protection thereof.

Fig. 1 shows a flow chart of the method for operating a vehicle according to an exemplary embodiment of the present invention.

In step 101, a route to be travelled by a vehicle is planned with the aid of a driving assistance device or navigation device of the vehicle. During route planning, besides taking into account factors such as desired start/stop positions, distance of travel and traffic congestion, road surface information of different routes may also be taken into account through interaction with a historical database (such as a cloud sharing platform). As an example, a route that reduces road surface jolting may be selected automatically as the route to be travelled from at least one alternative route. It is also conceivable to select different travel routes for different passenger states. For example, if the passengers include a pregnant woman or an elderly person in poor physical condition, the distance of travel and congestion situation might be of secondary importance to passenger comfort. However, if the driver is the only person in the cabin and he or she is commuting, the commuting time and road conditions are of primary importance, so some passenger comfort in particular can be sacrificed to increase time efficiency.

Next, in step 102, the historical database is searched, in order to judge whether a historical route coinciding with at least a part of the planned route to be travelled exists. For example, it is possible to check: whether the planned route is able to cover at least one geographical position point where historical road surface data upload took place at a previous time.

If no matching historical route is found in the historical database, this indicates that the planned route is completely unfamiliar to the historical database, so it can be concluded that in terms of providing a passenger comfort strategy, historical experience is unable to provide any auxiliary support. Thus, next, in step 106, road surface information is detected in real time and dynamical parameters of the vehicle are calculated on this basis, and shock absorption characteristics of the vehicle are adjusted dynamically according to the dynamical parameters calculated in real time.

If a matching historical route exists in the historical database, this indicates that the same road section has already been travelled by another vehicle and/or the vehicle itself at a previous time, and a corresponding solution for providing passenger comfort has been uploaded. Thus, the vehicle can be made to travel along the planned route in step 103, and road surface data along the route to be travelled can be acquired in step 104.

Next, in step 105, communication with the historical database can take place again, in order to compare road surface information acquired in real time with historical road surface data, and judge whether they are in agreement. Here, for example, a judgement can be made as to whether the degree of agreement between the acquired road surface information and the historical road surface data satisfies a predefined condition (e.g. whether it is higher than a predefined threshold).

If it is judged in step 105 that agreement is lacking or that the degree of agreement fails to satisfy the predefined condition (e.g. is lower than the threshold), this indicates that although road surface data and a corresponding adjustment strategy have been recorded for this road section at a historical time, it is highly likely that the road surface state of the road section has changed because the road section has undergone maintenance or because of the weather, and consequently, even though the course of the road that is recorded is the same, the road surface information cannot be matched to the historical road surface data. In this case, in step 106, road surface information of the road surface to be travelled by the vehicle is detected in real time with the aid of sensing means outside and/or inside the vehicle; for example, speed information, acceleration information and travelling attitude information of the vehicle are acquired in real time with the aid of a wheel speed sensor, and road surface information is deduced on the basis of these items of information in particular. On this basis, dynamical parameters of the vehicle are then calculated, and the shock absorption characteristics of the vehicle are adjusted dynamically according to the dynamical parameters calculated in real time. If it is judged in step 105 that the road surface information is in agreement with the historical road surface data or that the degree of agreement therebetween is higher than the threshold, this indicates that compared with the time of the historical record, the road surface state of the road section has not changed noticeably, so the existing solution in the historical database is still valid. In this case, in step 107 an initial framework of a shock absorption model of the vehicle can be established on the basis of the existing solution in the historical database.

Next, in step 108, based on the currently obtained adjustment strategy, it is further necessary to acquire vehicle state information. In the sense of the present invention, vehicle state information is in particular understood to mean configuration information of the vehicle itself and passenger state information. Configuration information of the vehicle itself for example includes the vehicle model, vehicle weight, position of the centre of gravity of the vehicle, etc. Passenger state information for example includes the number of passengers, passenger distribution, passenger weight, passenger physical condition, passenger posture, etc. As an example, in step 108 vehicle state information can in particular be acquired multiple times at fixed time intervals, in order to check whether a change in vehicle load has been caused for example by a change in position or movement of a person, etc.

In step 109, the adjustment strategy obtained in step 107 or 106 can be optimized on the basis of the acquired vehicle state information. Here, an active suspension apparatus and a seat shock absorption apparatus of the vehicle can be adjusted in a coupled manner; for example, in particular, shock absorption amount is distributed to the active suspension apparatus and the seat shock absorption apparatus according to vehicle load information. As an example, different shock absorption amounts can be provided to the seat shock absorption apparatus for different seat positions, e.g. such that rear seat passengers experience a more noticeable shock absorption effect than the driver. As another example, control signals for the seat shock absorption apparatus and active suspension apparatus can be re-generated on the basis of the acquired passenger distribution after a fixed time interval, so that the adjustment strategy can adapt to changes in passenger position and/or posture with time. As another example, if it is detected that there are no passengers in the cabin, the seat shock absorption function is automatically not activated, for more energy-saving and efficient operation. In addition, it is also possible to calculate adjustment factors for the active suspension apparatus and a wheel hub driving apparatus on the basis of information such as the weight and model number of the vehicle itself, and to perform re-fitting of initially established shock absorption damping, rigidity and local trajectory curves (e.g. acquired directly from the historical database) on the basis of the adjustment factors.

In step 110, the optimized adjustment strategy can be used to operate the vehicle.

Fig. 2 shows a flow chart of one method step of the method for operating a vehicle according to an exemplary embodiment of the present invention.

In step 201, road surface data acquired in real time along the planned route to be travelled is compared with historical road surface data.

If the judgement result obtained indicates agreement, then in step 203, a first adjustment mode of an adjustment strategy is enabled; in this adjustment mode, the shock absorption characteristics of the vehicle are adjusted according to pre stored dynamical parameters. For example, a damping characteristic curve and a rigidity characteristic curve recorded in a known solution can be called directly from the historical database, and applied to the active suspension apparatus of the vehicle. At the same time, the vehicle can also be operated directly according to a trajectory recorded in the historical database.

If it is judged that agreement is lacking, then in step 202, a second adjustment mode of the adjustment strategy is enabled; in this adjustment mode, dynamical parameters of the vehicle are calculated in real time, and the shock absorption characteristics of the vehicle are thereby adjusted dynamically. For example, it is possible to adjust parameter settings of the active suspension apparatus with reference to the acquired road surface information in the following step 211, and independently adjust the motion of each wheel with the aid of a distributed wheel hub driving apparatus in step 212; in addition, it is also possible to adjust a local motion trajectory of the vehicle according to a road surface contour ahead in step 213.

Next, in step 214, updated road surface information and an associated adjustment strategy can be uploaded to and/or stored in the historical database, thereby forming a new solution in the historical database, for the vehicle itself and/or another vehicle to directly refer to or call during subsequent operation.

Fig. 3 shows a block diagram of an exemplary vehicle 10 comprising a device 30 for operating a vehicle according to the present invention. As shown in Fig. 3, the vehicle 10 comprises a vehicle body 2 fitted with wheels 3; the wheels 3 can be driven with the aid of a driving apparatus 1 (e.g. a drive shaft) and at the same time are supported by means of the driving apparatus with the aid of an active suspension apparatus 330. The active suspension apparatus 330 performs shock absorption for the vehicle body 2 relative to the wheels 3 by means of corresponding spring and/or damping units. In addition, seat shock absorption apparatuses 340 are mounted between the vehicle body 2 and the seats; the seat shock absorption apparatuses 340 perform shock absorption between the vehicle body 2 and the seats by means of corresponding spring and/or damping units.

In this embodiment, the device 30 for operating a vehicle is a component part of the vehicle 10; the device 30 comprises acquisition modules 301 - 304, an adjustment module 300 and execution modules 330, 340, 350. The adjustment module 300 further comprises a control module 310 and an optimization module 320.

The acquisition modules 301 - 304 are configured to acquire road surface information of a route to be travelled by the vehicle 10, and state information of the vehicle 10; for this purpose, the acquisition modules may comprise an external camera unit 301, an internal camera unit 302, a wheel sensor unit 303 and a seat sensor unit 304. The external camera unit 301 is configured to capture a surrounding environment of the vehicle 10, and in particular is configured to capture an image of a road surface ahead of the vehicle 10, and can obtain a contour of a road that is about to be travelled on the basis of the road surface image by means of a corresponding image processing unit (not shown separately), and thereby determines by analysis the variation in height of the road surface relative to a specific plane. In addition, it is also conceivable to scan the road surface with the aid of another on-board sensor such as a laser radar, ultrasound sensor or infrared sensor and thereby obtain road surface information.

Besides being able to anticipate the road surface situation ahead in the form of a road preview by means of the external camera unit 301, it is also possible to sense changes in acceleration of the wheels along the longitudinal axis and/or transverse axis by means of the wheel sensor unit 303 arranged on the vehicle chassis (in particular a wheel 3), and contour information of the road surface to be travelled can thereby be calculated indirectly. In addition, it is also possible to determine a road surface topology by analysing pitching motion, lateral tilting motion and/or yawing motion of the vehicle.

The internal camera unit 302 is configured to capture an image of the interior of the vehicle 10, and thereby identify a load state, in particular a passenger state, in the cabin. For example, by analysing the captured image, it is possible to learn the following information: the number of passengers, passenger distribution, passenger weight, passenger physical condition, passenger posture, etc.

In addition, it is also possible to identify a load state of the vehicle 10 with the aid of the seat sensor unit 304 arranged at a seat of the vehicle 10; for example, by measuring the weight of a passenger sitting on the seat, the distribution of the load of the vehicle 10 at different positions can be determined. To obtain overall load state information of the vehicle 10, it is for example also possible to monitor parameters of the vehicle 10 such as drive torque, braking torque and acceleration of accelerator pedal position by means of corresponding sensors.

The control module 310 receives road surface information of the route to be travelled by the vehicle 10 from at least one acquisition module 301, 303. In addition, the control module 310 communicates with the historical database arranged in a cloud sharing platform 4, and can thereby compare the acquired road surface information with historical road surface data. On the basis of the comparison result, the control module 310 requests an adjustment strategy for enabling the vehicle 10 to provide passenger comfort on the route to be travelled.

After receiving the corresponding adjustment strategy, the control module 310 transmits the adjustment strategy to the optimization module 320, in order to optimize the adjustment strategy there on the basis of vehicle state information, such that the adjustment strategy finally obtained is not only adapted to the state of the road surface to be travelled, but can also be matched at the same time to the current configuration and load state of the vehicle 10. As an example, the optimization module 320 acquires signals of acceleration along the longitudinal axis and/or transverse axis of the vehicle 10 from the wheel sensor unit 303 and seat sensor unit 304 separately; these acceleration signals give rise to deviation of the vehicle body 2 and seat respectively. By analysing these two types of acceleration signals in the optimization module 320, control signals for the active suspension apparatus 330 and seat damping apparatus 340 can be generated. These control signals ensure rational distribution of the shock absorption amounts (e.g. rigidity and/or damping signals) applied to the active suspension apparatus 330 and seat damping apparatus 340, so that at the same time as shocks to the vehicle body are reduced by means of the active suspension apparatus 330, a compensating shock absorption effect is produced by means of the seat shock absorption apparatus 340 with reference to local load information, so that shock absorption action forces for a specific load state are superimposed on vehicle body shock absorption. For example, when a certain degree of rebound of the frame 2 is caused by the active suspension apparatus 330, the amount of rebound can be compensated for or superimposed with the aid of the seat shock absorption apparatus 340 with reference to local load information.

Finally, the vehicle 10 can be operated according to the optimized adjustment strategy by means of the corresponding execution modules 330, 340, 350. Here, besides being able to adjust the active suspension apparatus 330 and seat shock absorption apparatus 340, the motion of each wheel 3 is also independently adjusted by means of the torque vector distribution of the distributed wheel hub driving apparatus 350, and it is thereby possible for example to independently control the steering and rotation speed of each wheel 3; this exhibits flexibility especially in terms of local avoidance of obstacles on the ground. At the same time, because the motion of the wheels 3 can be precisely controlled one by one, the stability of the vehicle body 2 as a whole is also improved to a certain extent.

Fig. 4 shows a schematic drawing of the method according to the present invention being used in an exemplary application scenario.

Multiple vehicles 10, 11, 12 are shown in this exemplary application scenario; these vehicles 10, 11, 12 exchange data with the cloud sharing platform 4 via a wireless communication connection. The historical database is arranged in the cloud sharing platform 4, wherein, for example, multiple geographical position coordinates are stored in the form of a list or a point set, while an adjustment strategy for providing passenger comfort is also correspondingly stored for each of the geographical position coordinates.

As an example, the vehicles 11, 12 detect that a bump 41 or a pothole 42 is present on a road surface to be travelled by means of their own optical sensor units (e.g. camera units, laser radar, infrared sensors, etc.), so the vehicles 11,

12 analyse these ground states 41, 42 using image processing technology, in order to calculate a height characteristic of this local ground contour relative to a specific plane. It is thereby possible for example to calculate control signals for execution mechanisms such as the active suspension apparatus, the distributed wheel hub driving apparatus and a steering apparatus with the aid of an artificial intelligence model. Upon reaching the geographical position of the ground bump 41 or pothole 42, the vehicles 11, 12 transmit control parameters and ground state information corresponding to the geographical position to the cloud sharing platform 4 with the aid of a communication unit.

The vehicle 10 represents a vehicle travelling along a planned route; while travelling, the vehicle 10 can continuously compare acquired ground state information with historical road surface data in the cloud sharing platform 4. If matching historical road surface data is present in the cloud sharing platform 4, the vehicle 10 can call a corresponding solution from the cloud sharing platform, and apply it to itself while performing suitable adaptation with the aid of vehicle state information. Fig. 5 shows a schematic drawing of the method according to the present invention being used in another exemplary application scenario.

In this exemplary application scenario, the vehicle 10 has already obtained a corresponding adjustment strategy based on comparison with historical road surface data. As an example, it is found while performing the method according to the present invention that historical road surface data in agreement with a road surface state 51 of the route to be travelled exists in the historical database.

Thus, in terms of trajectory planning, a local travelling trajectory 501 can be called directly from the historical database, in order to utilize empirical data as much as possible to enable the vehicle 10 to avoid local road surface jolting. However, in this case, the vehicle 10 is not caused to travel in accordance with this called local travelling trajectory 501 directly; it is further necessary to finely adjust this known local travelling trajectory 501 with reference to state information of the vehicle 10 itself. In the sense of the present invention, the route to be travelled is understood as being a total itinerary between start and stop positions planned with the aid of a navigation system; this itinerary is generally shown on a map by multiple straight-line segments pointing from a starting point to an end point. The local travelling trajectory is understood as being a trajectory of vehicle motion along the route to be travelled; this is generally composed of trajectory points, and exhibits motion amplitude and direction characteristics in space.

As an example, in the historical database, the local travelling trajectory 501 has already been recommended to the vehicle 10, but taking into account a current vehicle configuration of the vehicle 10 (especially information such as vehicle dimensions, tyre width and wheel track), it is necessary to perform fine adjustment based on the local travelling trajectory 501, so as to obtain an optimized local travelling trajectory 502 or 503.

Although specific embodiments of the present invention have been described in detail here, they are only presented for the purpose of explanation, and should not be regarded as limiting the scope of the present invention. Various substitutions, changes and alterations could be conceived of without departing from the spirit and scope of the present invention.