Stepper motor ramp generation

Abstract

A method for generating stepper motor ramps and analyzing the motor torque required compared with the motor torque available wherein the generated ramp accelerates the motor as fast as possible while maintaining a user settable torque safety factor and/or safety margin. The method uses the minimum available stepper motor torque at the current motor speed to ultimately compute the maximum useable acceleration, uses the maximum acceleration to generate the next motor step time and hence the next motor velocity, computes the next velocity from the desired acceleration and the previous velocity and utilizes friction during deceleration of the motor. In particular, the method comprises determining the minimum available torque using the current motor velocity and the torque-speed characteristic of the motor, applying to the available torque a safety factor and then a safety margin to determine maximum useable torque wherein the safety factor is derived from motor information and the safety margin is derived from system information, calculating the maximum acceleration using the friction and moment of inertia of the system and the maximum usable motor torque, calculating the time duration of the next step for advancing the motor, repeating the foregoing steps to determine all steps in the ramps, and utilizing the generated motor ramps in advancing the stepper motor. The generated ramp always exploits the full drive capability of the stepper motor, and it provides a relatively constant margin between available torque and required torque during both acceleration and deceleration of the motor.