Stepper Motor

interface of the two stepper motors on the e-puck More...

Files
file	el_stepper_motor.h

Detailed Description

interface of the two stepper motors on the e-puck

Introduction

The e-puck is driven by two stepper-motors. The maximum speed of these motors are 1000 steps per second.

Example

Since these are stepper motors, it is possible to estimate the angle (and thus distance) traveled by each of the wheels.

In the following example, the robot does a counterclockwise rotation of 180 deg.

void Process_Rotate180(void*unused){
    int steps_l,steps_r;
    int steps_required;
    
    // turn off artificial motor acceleration so the rotation will stop immediately
    el_stepper_motor_options()->UseAcceleration = false;
    el_stepper_motor_options_apply();
    
    el_enable_stepper_motor();
    
    // reset step counters
    el_stepper_motor_set_steps( EL_STEPPER_MOTOR_LEFT, 0 );
    el_stepper_motor_set_steps( EL_STEPPER_MOTOR_RIGHT, 0 );
    
    el_set_wheel_speed( -250, 250 );// begin a counterclockwise rotation
    
    steps_required = EL_EPUCK_FULL_REVOLUTION_STEPS/2;
    
    // wait until the step difference reaching the required amount
    do{
    
        el_process_cooperate();
        
        steps_l = el_stepper_motor_get_steps(EL_STEPPER_MOTOR_LEFT);
        steps_r = el_stepper_motor_get_steps(EL_STEPPER_MOTOR_RIGHT);
        
    }while( (steps_r - steps_l) < steps_required );
    
    el_set_wheel_speed( 0, 0 );
    
    el_disable_stepper_motor();
}

Note: The step counters are 16-bit signed integers, so their limit (-32768 to 32767) will reach quickly if the robot keeps moving. If a long period of step counting is needed, one should read the step counters, add them to wider variables (e.g. long int) and then reset them before they are overflowed.