By wire control of braking and acceleration

Abstract

A rider surface maintenance vehicle with variable dynamic braking, in contrast to a mechanically-engaged braking system that uses a brake cable. A brake pedal engages a sensor that encodes the pedal position as an electronic signal. The electronic signal, along with the vehicle velocity, determines a machine deceleration rate, or braking rate, either by calculation, lookup table, or a combination of the two. The braking rate may be tuned so that the of the brake mimics or approximates the feel of a conventional mechanically-engaged brake that uses a brake cable. During stopping, once the vehicle passes below a threshold velocity, a parking brake is automatically engaged. The braking rate is converted to a duty cycle, and the braking is preferably accomplished by pulse width modulation (PWM) of an electrical load applied in parallel to the motor.

1 . (canceled)  
     
     
         2 . A method of providing an electrical braking function through an electrical motor in a surface maintenance vehicle to proximate the feel of a mechanical braking system, comprising the steps of: 
 a. engaging a brake pedal to initiate braking function;    b. sensing the position of the brake pedal and encoding the pedal position as an electronic signal;    c. sensing the vehicle velocity;    d. using said vehicle velocity and said signal, determining a desired machine deceleration rate to approximate the sensation of mechanical braking;    e. generating a series of pulses of frequency greater than the response frequency of the motor;    f. within each pulse defining the desired duty cycle to create an effective conductance;    g. applying the effective conductance in parallel with the motor to cause machine deceleration by dynamic braking; and    h. iteratively checking vehicle velocity and brake pedal position and correspondingly altering duty cycle to respond to demand for greater or lesser braking.    
     
     
         3 . The method of  claim 2 , wherein the determining step is performed by calculation.  
     
     
         4 . The method of  claim 2 , wherein the determining step is performed by lookup table.  
     
     
         5 . The method of  claim 2 , wherein the determining step is performed by a combination of calculation and lookup table.  
     
     
         6 . The method of  claim 2 , wherein the amplitude of each pulse is essentially constant and does not vary with duty cycle.  
     
     
         7 . The method of  claim 6 , wherein if the sensed vehicle velocity is below a predetermined threshold velocity, then a parking brake is engaged.  
     
     
         8 . The method of  claim 7 , wherein the parking brake is a solenoid-driven spring-loaded caliper brake pad.  
     
     
         9 . A method of providing an electrical braking function through an electrical motor in a surface maintenance vehicle to proximate the function of a mechanical braking system, comprising the steps of: 
 a. engaging a brake pedal to initiate braking function;    b. sensing the position of the brake pedal and encoding the pedal position as an electronic signal;    c. sensing the vehicle velocity;    d. using said vehicle velocity and said signal, determining a desired machine deceleration rate to approximate the sensation of mechanical braking;    e. generating an analog signal in response to the deceleration rate;    f. applying a voltage in response to the analog signal to the motor to cause machine deceleration by dynamic braking; and    g. iteratively checking vehicle velocity and brake pedal position and correspondingly altering the voltage to respond to demand for greater or lesser braking.    
     
     
         10 . An electrically powered surface maintenance machine with dynamic braking capable of proximating mechanical braking response, comprising: 
 a. an electric motor;    b. a brake pedal having a position sensor;    c. an encoder for converting the pedal position to an electrical pedal position signal;    d. a machine velocity sensor;    e. a braking rate controller capable of determining braking force tuned to approximate mechanical braking, in response to the electrical pedal position signal and the machine velocity;    f. a converter to translate braking rate to an effective electrical load to be applied in parallel to the motor;    g. an updater for iteratively checking the machine velocity and the pedal position and repeatedly adjusting the braking rate and thereby adjusting the effective electrical load applied in parallel to the motor.    
     
     
         11 . The machine of  claim 10 , wherein the effective electrical load is determined by a series of pulses of frequency greater than the response frequency of the motor.  
     
     
         12 . The machine of  claim 11 , wherein the effective electrical load is determined by the duty cycles of the pulses.  
     
     
         13 . The machine of  claim 12 , wherein the amplitude of the pulses is essentially constant and independent of the duty cycle.  
     
     
         14 . The machine of  claim 10 , wherein if the sensed machine velocity is below a predetermined threshold velocity, then a parking brake is engaged.  
     
     
         15 . The machine of  claim 14 , wherein the parking brake is a solenoid-driven spring-loaded caliper brake pad.