Dynamic Electric Drive Control

Abstract

A Light Electric Vehicle (LEV) 10, 20 includes two motors 24a, 24b and independent control of each motor. The two motors have different drive ratios (for example, gearing 26 or pulley/sprocket 28 ratios) or different efficiency versus RPM curves and are controlled to provide efficient operation over a wider speed range than possible with a single motor or two motors having the same efficiency at any given vehicle speed.

Claims

1. A Light Electric Vehicle (LEV), comprising: first and second wheels providing propulsion; a first electric motor coupled to drive the first wheel at a first speed versus efficiency curve; a second electric motor coupled to dive the second wheel at a second speed versus efficiency curve different from the first speed versus efficiency curve, the second electric motor having a different drive ratio and/or different motor performance characteristics than the first electric motor; and a processor configured to compute motor control signals for the first and second electric motors based on: throttle position; motor efficiency; and vehicle speed and acceleration.

2. The LEV of claim 1, wherein at least one of the first electric motor and the second electric motor are connected to corresponding ones of the first and second wheels by gears.

3. The LEV of claim 1, wherein at least one of the first electric motor and the second electric motor are connected to corresponding ones of the first and second wheels by a belt.

4. The LEV of claim 1, wherein at least one of the first electric motor and the second electric motor are connected to corresponding ones of the first and second wheels by a chain.

5. The LEV of claim 1, wherein the motor control signals comprise voltage and current provided to each motor.

6. The LEV of claim 1, wherein the motor control signals further depend on an efficiency variable which prioritizes efficiency versus vehicle speed.

7. A method for controlling a Light Electric Vehicle (LEV) having at least two electric motors individually coupled to drive the LEV, the method comprising: monitoring throttle position, motor efficiency, and vehicle speed and acceleration; comparing efficiencies of the two or more motors as a function of speed and load to determine efficiency ratios; and adjusting voltage and current to each of the electric motors based on the efficiency ratios to optimize performance.

8. The method of claim 7, further including: setting an efficiency variable for the efficiency ratio wherein minimum setting prioritizes efficiency and maximum prioritizes vehicle speed; and based on the vehicle load and efficiency variable, dynamically adjusting the efficiency ratios using control options to most accurately meet the desired performances subject to total vehicle efficiency of the vehicle drive and variable setting.

9. A method for controlling a Light Electric Vehicle (LEV), the method comprising: providing a vehicle having at least two motors having different gear ratios and/or different motor performance characteristics; monitoring throttle position to determine desired performance; monitoring vehicle speed and rate of acceleration or deceleration to determine measured performance; monitoring running efficiency and rate of change of efficiency of each motor based on speed and/or current draw and/or temperature; comparing efficiencies of the two or more motors as a function of speed and load to determine efficiency ratios; inferring total vehicle efficiency by comparing the efficiency ratios to the motor performance characteristics; inferring vehicle load by comparing throttle position to measured performance to total vehicle efficiency; setting an efficiency variable for the efficiency ratio wherein minimum setting prioritizes efficiency and maximum prioritizes vehicle speed; based on the vehicle load and efficiency variable, dynamically adjusting the efficiency ratios using control options to most accurately meet the desired performances subject to total vehicle efficiency of the vehicle drive and variable setting; and based on the adjusted efficiency ratios, a controller continuously measuring and adjusting voltage and current to each of the motors.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0017] The above and other aspects, features and advantages of the present invention will be more apparent from the following more particular description thereof, presented in conjunction with the following drawings wherein:

[0018] FIG. 1 shows the power and efficiency versus RPM of a typical Permanent Magnet Direct Current (PMDC) motor.

[0019] FIG. 2 shows a bicycle having two motors according to the present invention.

[0020] FIG. 3 shows a three or four wheel vehicle having two motors according to the present invention.

[0021] FIG. 4 shows a method according to the present invention.

[0022] Corresponding reference characters indicate corresponding components throughout the several views of the drawings.

BEST MODE FOR CARRYING OUT THE INVENTION

[0023] The following description is of the best mode presently contemplated for carrying out the invention. This description is not to be taken in a limiting sense, but is made merely for the purpose of describing one or more preferred embodiments of the invention. The scope of the invention should be determined with reference to the claims.

[0024] Where the terms about or generally are associated with an element of the invention, it is intended to describe a feature's appearance to the human eye or human perception, and not a precise measurement. Either gear ratio or pulley/sprocket size differences are referred to as drive ratio and the method of the present invention is equally applicable to a motor couple to vehicle wheels through gear, belts, or chains.

First Embodiment

[0025] FIG. 2 shows a bicycle 10 having 10 electric motors 12a and 12b (for example, hub motors), the first motor 12a driving a front wheel 12a, and a second motor 12b independently driving a rear wheel 12b. The two electric motors 12a and 12b allow for the rear motor 12b to be geared for more torque and lower speed (creating a first gear) and the front motor 12a to be geared for higher speed with greater efficiency (creating a second gear). A processor (or controller) 16 monitors rider inputs (for example, throttle position, pedal torque, brake application, etc.) and vehicle data (for example, motor efficiency and vehicle speed and acceleration) and determines how to most efficiently power the bicycle 10 using a battery 18 providing current and voltage to the motors 12a and 12b. The controller may further have stored efficiency versus RPM data for the motors 12a and 12b. Overlapping the motors 12a and 12b with different applications of primary power (both current and voltage) allocation allows for the bicycle 10 to maintain maximum efficiency no matter what the load or slope it must overcome. An additional benefit of this configuration is that it can be installed in a conventional bicycle frame design without any customization.

Second Embodiment

[0026] Alternately, motors can be connected to the wheels or axles through gears, chains or belts. When separate motors provide torque to right and left wheels of a three or four wheeled vehicle, an additional software function is incorporated to blend power on start up so that the low speed wheel doesn't receive so much power that it begins to steer the vehicle.

Third Embodiment

[0027] FIG. 3 shows a front or rear view of a three or four wheeled vehicle 20 having a seat 36, a front wheel 22a, and two motors 24a and 24b independently powering two independent wheels 22b and 22c. The motor 24a drives the wheel 22b through gears 26 and the motor 24b drives the wheel 22c through chain or belt 28. Sprague (or one way) clutches 30 may reside between the motors 24a and 24b and the axles 34a and 34b respectively to decouple a motor not providing torque to the wheels 22b and 22c. The motors 24a and 24b may be controlled as described for FIG. 2 to optimize efficiency.

[0028] A blend of the configurations may be used because the motor style used in the vehicle 20 may often generate low end torque more efficiently. Therefore some embodiments may have a first gear which is chain or belt driven and a second gear which is hub motor driven.

[0029] Additionally, for heavier applications, each wheel might have its own complete drive. That is, a wheel may be driven by one hub motor which has a secondary motor connected to it via a chain or belt. This gives the benefit of redundant drives in the event of a single component failure.

[0030] A method according to the present invention is shown in FIG. 4. The method includes providing a vehicle having at least two motors having different gear ratios and/or different motor performance characteristics at step 100, monitoring throttle position to determine desired performance at step 102, monitoring vehicle speed and rate of acceleration or deceleration to determine measured performance at step 104, monitoring running efficiency and rate of change of efficiency of each motor based on speed and/or current draw and/or temperature at step 106, comparing efficiencies of the two or more motors as a function of speed and load to determine efficiency ratios step 108, inferring total vehicle efficiency by comparing the efficiency ratios to the motor performance characteristics at step 110, inferring vehicle load by comparing throttle position to measured performance to total vehicle efficiency at step 112, setting an efficiency variable for the efficiency ratio wherein minimum setting prioritizes efficiency and maximum prioritizes vehicle speed at step 114, based on the vehicle load and efficiency variable, dynamically adjusting the efficiency ratios using control options to most accurately meet the desired performances subject to total vehicle efficiency of the vehicle drive and variable setting at step 116, and based on the adjusted efficiency ratios, the controller continuously measuring and adjusting voltage and current to each of the motors at step 118.

INDUSTRIAL APPLICABILITY

[0031] The present invention finds industrial applicability in the field of electric vehicles.

SCOPE OF THE INVENTION

[0032] While the invention herein disclosed has been described by means of specific embodiments and applications thereof, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims.