Control and force-sensing method and apparatus for motors

A method of accelerating a stepper motor through a range of velocities extending from a first rotational velocity to a second rotational velocity different from the first wherein the stepper motor is responsive to a drive waveform comprising a sequence of stair steps, each having a step size and a step duration, and further wherein the step size is selectable to designate the number of stair steps by which a cycle of the drive waveform is generated, the method comprising the steps of

• maintaining the step size in the drive waveform at a first predetermined value for rotational velocities within a first portion of the rotational velocity range;
• concurrently decreasing the step duration of each stair step in the drive waveform until the rotational velocity of the stepper motor enters a second portion of the rotational velocity range above the first portion of the rotational velocity range;
• maintaining the step size at a second predetermined value, greater than the first predetermined value, over the second portion of the rotational velocity range;
• concurrently decreasing the step duration of each stair step in the drive waveform until the rotational velocity of the stepper motor enters a next portion of the rotational velocity range above the second portion;
• sequentially modifying the step size for subsequent portions of the rotational velocity range, and varying the step duration for each step of the drive waveform thereof until the rotational velocity of the stepper motor is substantially equal to the second rotational velocity, so that the stepper motor is caused to be accelerated by a number of progressive step sizes and a varying step duration.

A method for driving a stepper motor for rotation at a rotational velocity designated by a command velocity signal and which is selected from a range of rotational velocities, wherein the stepper motor is responsive to a drive waveform which includes a sequence of stair steps each having a step size and a step duration, the method comprising the steps of

• generating step size data and step duration data in response to the command velocity signal and in accordance with the relative position of the selected rotational velocity in the range of rotational velocities, whereby data corresponding to small step sizes are generated for lower selected rotational velocities, and whereby data corresponding to large step sizes are generated for higher selected rotational velocities;
• and
• generating the sequence of stair steps in response to the step size and step duration data wherein each stair step in the sequence has a designated relative amplitude and duration, wherein the relative amplitudes emulate points along a sinusoidal-like drive curve which are sequentially spaced apart in phase at a designated regular interval, the magnitude of the regular interval being specified by the step size data, and further wherein the duration of each stair step is specified by the step duration data, whereby for lower selected rotational velocities the sequence of stair steps includes a large number of drive pulses having amplitudes corresponding to closely-spaced points in the sinusoidal drive curve which sequentially define a slowly varying sinusoidal-like function, and whereby, for higher selected rotational velocities, the sequence of stair steps includes a small number of drive pulses having amplitudes corresponding to more widely spaced points on the sinusoidal-like drive curve, which sequentially define a more rapidly varying sinusoidal-like function.

An apparatus responsive to a set of drive instructions for controlling the rotation of a shaft of a stepper motor in a number of predetermined modes, wherein the stepper motor is responsive to a drive waveform having a sequence of stair steps and is capable of rotation at a rotational velocity which is selected from a range of velocities, the apparatus comprising

• means responsive to a set of drive instructions for generating a sequence of step size and step duration data, wherein the step size and step duration data respectively designate relative amplitude and relative duration magnitudes and are generated as a function of the particular mode designated by the drive instructions;
• and
• means responsive to the sequence of step size and step duration data for generating the sequence of stair steps, whereby the duration of each stair step in the drive waveform is determined by the step duration data;
• wherein the drive instructions designate rotation by the stepper motor in a sequence of rotational velocities selected from the range of velocities, the range of velocities having a lower limit and an upper limit, and further wherein the step size and step duration data generating means include
• means for determining the relative position within the range of velocities of each rotational velocity of the sequence of rotational velocities;
• and
• means responsive to the relative position, within the range of velocities, of each rotational velocity of the sequence of rotational velocities, for varying the step size and step duration data generated for each of the rotational velocities, whereby smaller step sizes are designated for the rotational velocities which are positioned toward the lower limit of the range of velocities and whereby larger step sizes are designated for the rotational velocities which are positioned toward the upper limit of the range of velocities.

An apparatus responsive to a set of drive instructions for controlling the rotation of a shaft of a stepper motor in a number of predetermined modes, wherein the stepper motor is responsive to a drive waveform having a sequence of stair steps and is capable of rotation at a rotational velocity which is selected from a range of velocities, the apparatus comprising

• means responsive to a set of drive instructions for generating a sequence of step size and step duration data, wherein the step size and step duration data respectively designate relative amplitude and relative duration magnitudes and are generated as a function of the particular mode designated by the drive instructions;
• and
• means responsive to the sequence of step size and step duration data for generating the sequence of stair steps, whereby the duration of each stair step in the drive waveform is determined by the step duration data;
• wherein the drive instruction designate an acceleration over an allotted time period from a first velocity to a second velocity, which is greater than the first, and further wherein the step size and step duration data generating means include
• means responsive to the first and second velocities and the allotted time period for generating a command table and a step duration table, wherein the command table includes a sequential designation of step size and a predetermined number of steps to be output having such step size;
• and further wherein the step duration table includes a sequence of step durations, each step duration being associated with one of the stair steps in the drive waveform;
• and means responsive to the command table and the step duration table for generating an acceleration sequence of step size data and acceleration sequence of step duration data correlated to the sequence of step size data, wherein the step size is kept constant for a predetermined number of steps while the step duration is varied for each step, whereby the step size is increased after each set of the predetermined number of steps is generated and whereby the step duration is decreased for each step generated as the stepper motor is accelerated between the first velocity and the second velocity.

An apparatus responsive to a set of drive instructions for controlling the rotation of a shaft of a stepper motor in a number of predetermined modes, wherein the stepper motor is responsive to a drive waveform having a sequence of stair steps and is capable of rotation at a rotational velocity which is selected from a range of velocities, the apparatus comprising

• means responsive to a set of drive instructions for generating a sequence of step size and step duration data, wherein the step size and step duration data respectively designate relative amplitude and relative duration magnitudes and are generated as a function of the particular mode designated by the drive instructions;
• and
• means responsive to the sequence of step size and step duration data for generating the sequence of stair steps, whereby the duration of each stair step in the drive waveform is determined by the step duration data;
• wherein the drive instructions designate a positional mode for placing the shaft of the stepper motor in a commanded angular position, the apparatus further including means for providing a position signal which is indicative of the actual angular position of the stepper motor shaft;
• and further wherein the step size and step duration generating means include
• means responsive to the position signal and to the commanded angular position for determining a positional difference quantity between the predetermined angular position and the actual angular position of the shaft;
• means responsive to the positional difference quantity for designating the number and size of the stair steps required to position the shaft at the commanded angular position;
• and
• means for controlling the stair step sequence generating means so that the generated sequence contains the designated number and size of steps.