Traction systems for electrically powered vehicles

Abstract

Fixed frequency, fixed duration pulse streams are used to control power switches for one or more electrical motors of electrically powered vehicles or hybrid vehicles having one or more electric motors. The advantages of a pulse system are increased power efficiency and system simplicity over analog systems. The capability of system calibration with a single pulse allows the system to be used under any conditions, and real time adaptation to changes in conditions. Such system and methods provide much improved acceleration over other electrical systems, by making the best use of the coefficient of starting or static friction. The systems and methods provide a non slip traction control system, and the use of an off state in the pulse stream is superior to the use of braking systems for the same purpose, which waste power and cause mechanical wear. In addition, related computer program products are described.

What is claimed is: 
     
         1 . A system for controlling power exchanged between an electro-magnetic conversion device and at least one drive wheel of a vehicle, the system comprising:
 an electromagnetic conversion device configured and arranged to exchange power between the drive wheel and the electromagnetic conversion device;   the wheel configured and arranged to exchange power between the wheel and the electromagnetic conversion device;   a controller configured and arranged to: (i) receive acceleration commands and wheel slip information for the wheel as inputs, and (ii) produce as an output a control signal for the electromagnetic conversion device to exchange power between the wheel and the electromagnetic conversion device, wherein the control signal includes a timing cycle with a series of pulses of fixed frequency and fixed duration within the timing cycle to cause power to flow within the electromagnetic conversion device during an ON component of the timing cycle, and further wherein a first pulse with wheel slip is measured by monitoring and recording a first time duration of the pulse until the wheel slips and a second recovery time duration of the pulse, and using these time durations to generate the subsequent pulses in the timing cycle; and   a power switch connected to the electromagnetic conversion device including an input to receive the control signal to place the switch in one of an ON state and an OFF according to the timing cycle.   
     
     
         2 . The system of  claim 1 , wherein the controller is configured and arranged to adjust he timing cycle of the pulses of fixed frequency and fixed duration. 
     
     
         3 . The system of  claim 2 , wherein the controller is configured and arranged to adjust the timing cycle based on a sensed coefficient of friction of the wheel. 
     
     
         4 . The system of  claim 1 , wherein the controller is configured and arranged to provide real time adjustment of the power exchanged with the wheel, wherein changing traction conditions can be accommodated. 
     
     
         5 . The system of  claim 1 , wherein the system is configured and arranged for automatic measurement, storage, and use of the pulse length for the ON pulse. 
     
     
         6 . The system of  claim 1 , wherein the system is configured and arranged for automatic measurement, storage, and use of the pulse length for the OFF pulse. 
     
     
         7 . The system of  claim 1 , wherein the wheel slip information comprises a coefficient of starting friction or coefficient of sliding friction. 
     
     
         8 . The system of  claim 1 , further comprising a second electromagnetic conversion device, a second wheel, and a second power switch, wherein the controller is configured and arranged to (i) receive acceleration commands and wheel slip information for the second wheel as inputs, and (ii) produce as an output a control signal for the second electromagnetic conversion device to exchange power between the second wheel and the second electromagnetic conversion device, wherein the control signal includes a timing cycle with a series of pulses of fixed frequency and fixed duration within the timing cycle to cause power to flow within the second electromagnetic conversion device during an ON component of the timing cycle, and wherein the second power switch is connected to the second electromagnetic conversion device and includes an input to receive the control signal to place the second power switch in one of an ON state and an OFF according to the timing cycle. 
     
     
         9 . The system of  claim 8 , further comprising a third electromagnetic conversion device, a third wheel, and a third power switch, wherein the controller is configured and arranged to (i) receive acceleration commands and wheel slip information for the third wheel as inputs, and (ii) produce as an output a control signal for the third electromagnetic conversion device to exchange power between the third wheel and the third electromagnetic conversion device, wherein the control signal includes a timing cycle with a series of pulses of fixed frequency and fixed duration within the timing cycle to cause power to flow to the third electromagnetic conversion device during an ON component of the timing cycle, and wherein the third power switch is connected to the third electromagnetic conversion device and includes an input to receive the control signal to place the third power switch in one of an ON state and an OFF according to the timing cycle. 
     
     
         10 . The system of  claim 9 , further comprising a fourth electromagnetic conversion device, a fourth wheel, and a fourth power switch, wherein the controller is configured and arranged to (i) receive acceleration commands and wheel slip information for the fourth wheel as inputs, and (ii) produce as an output a control signal for the fourth electromagnetic conversion device to exchange power between the fourth wheel and the fourth electromagnetic conversion device, wherein the control signal includes a timing cycle with a series of pulses of fixed frequency and fixed duration within the timing cycle to cause power to flow to the fourth electromagnetic conversion device during an ON component of the timing cycle, and wherein the fourth power switch is connected to the fourth electromagnetic conversion device and includes an input to receive the control signal to place the fourth power switch in one of an ON state and an OFF according to the timing cycle. 
     
     
         11 . The system of  claim 1 , wherein the duration of each pulse of the control signal is equal to a period of time between pulses in the timing cycle. 
     
     
         12 . The system of  claim 1 , wherein the number of pulses in a timing cycle varies from zero to a maximum number corresponding to an acceleration level of the electromagnetic conversion device from zero to a maximum acceleration level. 
     
     
         13 . The system of  claim 1 , further comprising a processing system to generate the control signal supplied to the power switch and to time the start and end of each pulse within the timing cycle. 
     
     
         14 . The system of  claim 1 , wherein the length of the timing cycle is constant and the acceleration of the vehicle is varied by changing the number of pulses from one timing cycle to another timing cycle. 
     
     
         15 . The system of  claim 10 , wherein the controller is configured and arranged to provide synchronization of pulses provided to the four electromagnetic conversion devices for synchronized four-wheel drive operation. 
     
     
         16 . The system of  claim 8 , wherein the controller is configured and arranged to detect which wheels have a minimum acceptable traction for inclusion in a synchronized power pulse exchanged with the wheels. 
     
     
         17 . The system of  claim 16 , wherein the detection of the minimum acceptable traction is based on a minimum time before a slide starts to occur. 
     
     
         18 . The system of  claim 17 , wherein the minimum time is about 15 milliseconds. 
     
     
         19 . The system of  claim 10 , wherein the controller is configured and arranged to detect which wheels have a minimum acceptable traction for inclusion in a synchronized power pulse exchanged with the wheels. 
     
     
         20 . The system of  claim 19 , wherein the detection of the minimum acceptable traction is based on a minimum time before a slide starts to occur. 
     
     
         21 . The system of  claim 20 , wherein the minimum time is about 15 milliseconds. 
     
     
         22 . A method for controlling the power exchanged between an electro-magnetic conversion device coupled to one or more wheels of an electrically powered vehicle and the one or more wheels, the method comprising:
 providing a timing cycle;   determining a desired acceleration rate for a vehicle powered by one or more electrically driven wheels;   generating a control signal including a series of pulses of fixed frequency and fixed duration within the timing cycle corresponding to the desired acceleration rate; and   supplying a control signal to an input of a power switch connected to one or more electro-magnetic conversion devices, each connected to a respective one of the one or more wheels, to place the switch in one of an ON state during each pulse and an OFF state after each pulse to cause power to flow within the respective electro-magnetic conversion device connected to each electrically driven wheel during the ON state and cause the respective electro-magnetic conversion device to exchange a desired power with each electrically driven wheel over the timing cycle; and further wherein a first pulse with wheel slip is measured by monitoring and recording a first time duration of the pulse until the wheel slips and a second recovery time duration of the pulse, and using these time durations to generate the subsequent pulses in the timing cycle.   
     
     
         23 . The method of  claim 22 , wherein the one or more electrically driven wheels comprises two wheels. 
     
     
         24 . The method of  claim 22 , wherein the one or more electrically driven wheels comprises four wheels. 
     
     
         25 . The method of  claim 22 , wherein providing the timing cycle includes establishing a timing cycle of a constant length and the power exchanged with each wheel is varied by changing the number of generated pulses from one timing cycle to another timing cycle. 
     
     
         26 . The method of  claim 23  wherein the duration of each pulse of the control signal is equal to a period of time between pulses in the timing cycle. 
     
     
         27 . The method of  claim 23  wherein the duration of each pulse of the control signal is less than or equal to a period of time between pulses in the timing cycle. 
     
     
         28 . The method of  claim 23  wherein the number of pulses in a timing cycle varies from zero to a maximum number corresponding to a power level of an electromagnetic conversion device from zero to a maximum power level. 
     
     
         29 . The method of  claim 22 , further comprising adjusting the timing cycle of the pulses of fixed frequency and fixed duration. 
     
     
         30 . The method of  claim 29 , wherein adjusting the timing cycle IS based on a sensed coefficient of friction of the driven wheel. 
     
     
         31 . The method of  claim 30 , wherein adjusting the timing cycle comprises real-time adjustment, wherein changing traction conditions can be accommodated. 
     
     
         32 . The method of  claim 22 , further comprising automatic measurement, storage, and use of the pulse length for the ON pulse. 
     
     
         33 . The method of  claim 22 , further comprising sensing wheel slip information, wherein the wheel slip information comprises a coefficient of starting friction or coefficient of sliding friction. 
     
     
         34 . The method of  claim 22 , wherein supplying the control signal comprises providing synchronization of pulses provided to two or more electromagnetic conversion device for synchronized two-wheel power exchange or four-wheel power exchange operation. 
     
     
         35 . The method of  claim 22 , further comprising detecting which wheels have a minimum acceptable traction for inclusion in a synchronized power pulse exchanged with the wheels. 
     
     
         36 . The method of  claim 35 , wherein detecting the minimum acceptable traction is based on a minimum time before a slide starts to occur. 
     
     
         37 . The method of  claim 36 , wherein the minimum time is about 15 milliseconds. 
     
     
         38 . A computer program product residing on a computer-readable storage medium having a plurality of instructions stored thereon, which when executed by a processing system, cause the processing system to:
 provide a timing cycle;   determine a desired acceleration rate for a vehicle powered by one or more electrically driven wheels;   generate a control signal including a series of pulses of fixed frequency and fixed duration within the timing cycle corresponding to the desired acceleration rate; and   supply a control signal to an input of a power switch connected to one or more electro-magnetic conversion devices, each connected to a respective one of the one or more wheels, to place the switch in one of an ON state during each pulse and an OFF state after each pulse to cause power to flow within the respective electro-magnetic conversion device connected to each electrically driven wheel during the ON state and cause the respective electromagnetic conversion device to exchange a desired power with each electrically driven wheel over the timing cycle; and further wherein a first pulse with wheel slip is measured by monitoring and recording a first time duration of the pulse until the wheel slips and a second recovery time duration of the pulse, and using these time durations to generate the subsequent pulses in the timing cycle.   
     
     
         39 . The computer program product of  claim 38 , wherein the computer-readable storage medium comprises flash memory. 
     
     
         40 . The computer program product of  claim 38 , wherein the computer-readable storage medium comprises ROM memory. 
     
     
         41 . The computer program product of  claim 38 , wherein the one or more electrically driven wheels comprises two wheels. 
     
     
         42 . The computer program product of  claim 38 , wherein the one or more electrically driven wheels comprises four wheels. 
     
     
         43 . The computer program product of  claim 38 , wherein providing the timing cycle includes establishing a timing cycle of a constant length and the power exchanged with each wheel is varied by changing the number of generated pulses from one timing cycle to another timing cycle. 
     
     
         44 . The computer program product of  claim 38 , wherein the duration of each pulse of the control signal is equal to a period of time between pulses in the timing cycle. 
     
     
         45 . The computer program product of  claim 38 , wherein the duration of each pulse of the control signal is less than or equal to a period of time between pulses in the timing cycle. 
     
     
         46 . The computer program product of  claim 38 , wherein the number of pulses in a timing cycle varies from zero to a maximum number corresponding to a power level of an electromagnetic conversion device from zero to a maximum power level. 
     
     
         47 . The computer program product of  claim 38 , further comprising an instruction to adjust the timing cycle of the pulses of fixed frequency and fixed duration. 
     
     
         48 . The computer program product of  claim 38 , further comprising an instruction to adjust the timing cycle based on a sensed coefficient of friction of the driving wheel. 
     
     
         49 . The computer program product of  claim 38 , further comprising an instruction to adjust the timing cycle for real-time adjustment, wherein changing traction conditions can be accommodated. 
     
     
         50 . The computer program product of  claim 38 , further comprising an instruction for automatic measurement, storage, and use of the pulse length for the ON pulse. 
     
     
         51 . The computer program product of  claim 38 , further comprising an instruction for automatic measurement, storage, and use of the pulse length for the OFF pulse. 
     
     
         52 . The computer program product of  claim 38 , wherein the wheel slip information comprises a coefficient of starting friction or coefficient of sliding friction. 
     
     
         53 . The computer program product of  claim 38 , further comprising an instruction for providing synchronization of pulses provided to two or more electromagnetic conversion device for synchronized two-wheel exchange or four-wheel exchange operation. 
     
     
         54 . The computer program product of  claim 38 , further comprising an instruction for detecting which wheels have a minimum acceptable traction for inclusion in a synchronized power pulse exchanged with the wheels. 
     
     
         55 . The computer program product of  claim 54 , wherein detecting the minimum acceptable traction is based on a minimum time before a slide starts to occur. 
     
     
         56 . The computer program product of  claim 55 , wherein the minimum time IS about 15 milliseconds.