IMPROVEMENTS RELATING TO VARIABLE SPEED CONTROL DEVICES

Abstract: Individual sets of data control points are illustrated on a typical torque profile of a brushless DC motor showing how the torque capability decreases with increase of speed of the motor. Each set effectively corresponds to a particular simulated gear setting for gear changes when driving a vehicle powered by such an electric motor. The envelope defined by the data control points for four "gear settings" are indicated by the reference numerals (I, II, III, IIII). The control equipment for driving the motor can then only operate within the particular set which is selected (by suitable programming of an electronic control unit). When the user senses that he has reached maximum speed under a particular set he can change to a new set and thus effectively move up a gear. The reverse will of course apply if there is a desire to decelerate. As the driver arranges to increase the speed of the car to a maximum he will move up through each of the four gears unitl the maximum available speed from the motor is achieved.

Description: Improvements relating to Variable Speed Control Devices This invention is concerned with means for providing a variable speed from a DC electric motor. Whilst the invention is concerned particularly with means for controlling the speed of a wheeled vehicle it is to be understood that the device can equally be used for speed and motion control purposes in relation to wheeled and tracked vehicles, marine craft, aviation applications and mechanical handling applications. According to the present invention there is provided a system for creating a variable speed control for the output drive of a DC electric motor wherein individual sets of data control points on a torque to RPM speed profile are predefined and set as operational parameters into control equipment for driving the motor, such that the motor can only be driven within the confines of the operational envelope of any particular set, and switch means is provided for switching between the separate sets of operational parameters as desired. This system can be used in particular to simulate the effect of gear changing in a conventional motor vehicle. It is therefore particularly suited for installation into so called "go-karts" which are provided for recreational and competitive track driving. As the user gains speed he can switch from one set of operational parameters to a new set and thus simulate the effect of changing from a lower to a higher gear. It is greatly preferred that the system should incorporate a variable position acceleration control device which is able to create a signal related to the position of the control device to determine the electrical current level supplied to the motor. This control device can then be used as a conventional accelerator when the system is incorporated into a vehicle. Ideally means will be provided to prevent switching between sets of operational parameters whilst the acceleration control device is creating an output signal . The system can be provided with a reversion set of data control points which define operational parameters for reverse drive of the motor. This enables a vehicle, in which the system is incorporated, to be driven in reverse. Preferably control means will be provided to prevent operation of the motor under the operational parameters of said reversion set until the motor has come to a standstill. The system may also incorporate a braking device which, when operated will send control signals to the motor drive to cause assisted regenerative braking of the motor. Preferably such a system would be arranged so that (when an acceleration control device is provided) the signal sent from the braking device will override any control signals delivered by said acceleration control device. In the preferred arrangement the sets of data control points will be programmed into an EPROM device. The EPROM device could be replaced by another in which alternative sets of operational parameters can be defined. This enables the overall control system to be modified, for example to allow for the different circumstances present in a track around which a vehicle might be driven. The system can then be adapted for a variety of tracks, as required. Ideally the system will include a display panel to indicate the current status of control devices within the system. It is also possible to provide a remote-control linkage apparatus connected to modify the status of the control device within the system upon receipt of signals from a remote-control operating device. A preferred embodiment of the invention will now be described in more detail with reference to the accompanying drawing which is a graph illustrating the torque/speed profile of a DC electric motor. The drawing illustrates a typical torque profile of a brushless DC motor illustrating how the torque capability decreases with increase of speed of the motor. One of the major objectives of this invention is to provide a means of simulating gear changes when driving a vehicle powered by such an electric motor. This is achieved by defining individual sets of data control points, wherein each set effectively corresponds to a particular gear setting. The envelope defined by the data control points for four "gear settings" are indicated by the reference numerals I, II, III, IIII. The control equipment for driving the motor can then only operate within the particular set which is selected (by suitable programming of an electronic control unit) . When the user senses that he has reached maximum speed under a particular set he can change to a new set and thus effectively move up a gear. The reverse will or course apply if there is a desire to decelerate. As the driver arranges to increase the speed of the car to a maximum he will move up through each of the four gears until the maximum available speed from the motor is achieved. Changing gear from one gear to the next can be achieved by pressing switches on the steering wheel of the vehicle, one being provided for upwards changing and the other for downwards changing. A separate switch will be provided to enable the system to operate in such a manner that the motor is reversed (once it has achieved stationary condition) , thus providing a reverse "gear" for the vehicle. The system can be operated so as to simulate an automatic gear box. This can be achieved by placing zero torque blips at specific points such that the drive reduces no torque for a fraction of a second. This gives the feeling of a gear change. It will be appreciated that the system does not need to be limited to four gear changes as the number can be increased or decreased as desired.

Claims: CLAIMS 1. A system for creating a variable speed control for the output drive of a DC electric motor wherein individual sets of data control points on a torque to RPM speed profile are predefined and set as operational parameters into control equipment for driving the motor, such that the motor can only be driven within the confines of the operational envelope of any particular set, and switch means is provided for switching between the separate sets of operational parameters as desired. 2. A system according to Claim 1, wherein a variable position acceleration control device is provided which is able to create a signal related to the position of the control device to determine the electrical current level supplied to the motor. 3. A system according to Claim 2, wherein means is provided to prevent switching between sets of operational parameters whilst the acceleration control device is creating an output signal. 4. A system according to any one of Claims 1 to 3 , wherein the sets of data control points are programmed into an EPROM device. 5. A system according to any one of Claims 1 to 4, wherein a reversion set of data control points defines operational parameters for reverse drive of the motor. 6. A system according to Claim 5, wherein control means is provided to prevent operation of the motor under the operational parameters of said reversion set until the motor has come to a standstill . 7. A system according to any one of Claims 1 to 6, wherein a braking device is provided which, when operated, will send control signals to the motor drive to cause assisted regenerative braking of the motor. 8. A system according to the combination of Claims 2 and 7, arranged so that the signal sent from the braking device will override any control signals delivered by said acceleration control device. 9. A system according to any one of Claims 1 to 8, including a display panel to indicate the current status of control devices within the system. 10. A system according to any one of Claims 1 to 9, including remote-control linkage apparatus connected to modify the status of the control device within the system upon receipt of signals from a remote-control operating device . 11. A system for creating a variable speed control for the output drive of a DC electric motor . substantially as herein described with reference to the accompanying drawings . 12. Any novel combination of features of a system for creating a variable speed control for the output drive of a DC electric motor substantially as herein described and/or with reference to the accompanying drawings.

Inventors: LEWIS-BOYLE DAVID, LINDSAY ROBERT WILLIAM, LEWIS-BOYLE, DAVID, LINDSAY, ROBERT, WILLIAM
Applicants: LEWIS BOYLE DAVID, LINDSAY ROBERT WILLIAM, LINTEC INTERNATIONAL LIMITED, LEWIS-BOYLE, DAVID, LINDSAY, ROBERT, WILLIAM
Application year: 1999
Main classification: B60L15
IPC codes: B60L15