Electric Vehicle Control

• US 20100168946A1
• Filed: 12/31/2009
• Published: 07/01/2010
• Est. Priority Date: 12/31/2008
• Status: Active Grant

• Current Assignee: Mark Snyder
• Original Assignee: Mark Snyder
• Inventors: Snyder, Mark
• Granted Patent: US 8,326,502 B2
• Time in Patent Office: Days
• US Class Current: 701/22
• CPC Class Codes: B60L 15/2009 for braking
• CPC Class Codes: B60L 2240/16 longitudinal
• CPC Class Codes: B60L 2240/18 lateral
• CPC Class Codes: B60W 2520/105 Longitudinal acceleration
• CPC Class Codes: B60W 2520/125 Lateral acceleration
• CPC Class Codes: F16H 2059/663 Road slope
• CPC Class Codes: F16H 59/48 Inputs being a function of acceleration
• CPC Class Codes: F16H 59/66 Road conditions, e.g. slope, slippery
• CPC Class Codes: F16H 61/0213 characterised by the method for generating shift signals
• CPC Class Codes: H02P 6/182 using back-emf in windings
• CPC Class Codes: Y02T 10/64 Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/72 Electric energy management in electromobility

Abstract

A method for controlling an electric vehicle includes computing an electric motor RPM based on a computed Back Electromotive Force (BEMF). Modern electric vehicle designs include intelligent control of the electric motors and transmissions to respond to operator controls and provide efficient operation to extend battery life. An accurate measure of motor RPM is required for such control. Various methods are available for obtaining motor RPM, but most require external sensors susceptible to damage from road debris and the like. The BEMF is proportional to motor speed and independent of motor load. The BEMF may further be computed from the difference between IR loss and motor voltage. The motor RPM is them computed from BEMF using data recorded for the individual motor.

Claims

1. A method for estimating electric motor RPM based on a computed Back Electromotive Force (BEMF) of the electric motor, the method comprising:

obtaining RPM verus the BEMF data for the electric motor comprising;

rotating the motor shaft of the electric motor over an RPM range covering the normal operating range of the electric motor;

measuring BEMF versus RPM over the RPM range; and

recording the BEMF versus RPM data for later real time use;

estimating a real time BEMF of the electric motor during the later use of the electric motor, comprising;

measuring a motor voltage at electric motor terminals;

measuring a motor current through the electric motor corresponding to the motor voltage measurement;

computing IR loss by multiplying the motor current times a dynamic internal resistance of the electric motor; and

computing the BEMF by subtracting the IR loss from the motor voltage;

estimating the electric motor RPM by comparing the real time BEMF to the recorded BEMF versus RPM data; and

providing the estimated RPM to an intelligent controller to optimally control the motor.

2. The method of claim 1, further including providing the estimated RPM to an intelligent controller to optimally control a transmission.

3. A method for obtaining an adjusted operator signal to an electronic controller to provide power and regenerative braking which mimic the position of a power control operator interface and a braking control operator interface, the method comprising:

measuring positions of a power actuator and/or a braking actuator;

converting the positions to a power signal and a braking signal;

processing the power signal and the braking signal to obtain adjusted power and braking signal to provide a desired acceleration or braking compensating for vehicle speed, transmission gearing, road incline, etc.; and

providing current to a motor based on the adjusted power and braking signal.

4. A method for determining optimal shift points, the method comprising:

measuring X, Y, and Z accelerometers to obtain Xm, Ym, and Zm accelerometer measurements;

computing a vehicle incline from the Y and Z accelerometer measurements;

using the vehicle incline to correct the X accelerometer measurement for the vehicle incline to obtain actual fore-aft vehicle acceleration; and

determining whether or not to shift the transmission based on the incline and for-aft acceleration.