Method for adaptively driving a stepper motor, and corresponding device

Patent metadata

Field	Value
Publication number	US-10248135-B2
Application number	US-201715608596-A
Country	US
Kind code	B2
Filing date	May 30, 2017
Priority date	Nov 4, 2016
Publication date	Apr 2, 2019
Grant date	Apr 2, 2019

Abstract

A stepper motor is driven according to step driving modes including a full-step driving mode, a half-step driving mode and micro-stepping modes. The stepper motor may also be driven in an acceleration phase. A method of controlling the stepper motor includes controlling the current step driving mode of the motor by a processing unit. During the acceleration phase of the stepper motor and the stepper motor being in driven in a current step driving mode other than the full-step driving mode, the processing unit tests, after each speed increase, if a remaining computing power of the processing unit is sufficient for control of the stepper motor to remain in the current step driving mode, and if not the processing unit, in presence of a first switching condition, switches control of the stepper motor to the driving mode having the closest coarser step.

First claim

The invention claimed is:

1. A method for driving a stepper motor, comprising:
controlling the stepper motor in a current step driving mode of the stepper motor and in an acceleration phase of the stepper motor, the current step driving mode including a full-step driving mode, a half-step driving mode, and micro-stepping driving modes;
determining, if the current step driving mode is not the full-step driving mode and the stepper motor is being controlled in the acceleration phase, after each speed increase of the stepper motor whether a remaining computing power associated with controlling the stepper motor in the current step driving mode is sufficient for the stepper motor to remain being controlled in the current step driving mode; and
switching to one of the full-step, half-step, and micro-stepping driving modes having a closest coarser step in presence of a first switching condition in response to determining the remaining computing power is not sufficient for the stepper motor to remain being controlled in the current step driving mode, wherein switching to the one of the step full-step, half-step, and micro-stepping driving modes having a closest coarser step in presence of the first switching condition further includes said first switching condition including a correspondence of a current position of the motor in said current step driving mode with a position of the motor defined in said one of the full-step, half-step, and micro-stepping driving modes having the closest coarser step.

2. The method according to claim 1 , wherein controlling said stepper motor comprises controlling motor phases of the stepper motor, and wherein switching to one of the full-step, half-step, and micro-stepping driving modes having a closest coarser step in presence of the first switching condition comprises said first switching condition further including a minimum current gap on the motor phases.

3. The method according to claim 1 , wherein determining whether the remaining computing power associated with controlling the stepper motor in the current step driving mode is sufficient comprises:
evaluating a computing time needed to determine control parameters to be applied to the stepper motor in order for the stepper motor to reach a next position in said current step driving mode; and
determining a switching time required by the stepper motor to switch to said next position taking into account a current speed of the stepper motor; and
determining the remaining computing power is sufficient for remaining in said current step driving mode if said switching time is greater than or equal to said computing time plus a first margin.

4. The method according to claim 3 , wherein determining the remaining computing power is sufficient further comprises the first margin being greater than a first parameter equal to a length of a micro-step in said current step driving mode divided by the product of an acceleration and said switching time.

5. The method according to claim 4 , further comprising, in absence of said first switching condition, controlling the stepper motor in said current step driving mode for at least one new step in said current step driving mode, and wherein determining the remaining computing power comprises determining a value of said first margin that allows for performing said at least one new step in said current step driving mode.

6. The method according to claim 1 , further comprising controlling the stepper motor in a deceleration phase, wherein the controlling the stepper motor in the deceleration phase comprises, if the stepper motor is being controlled in the current step driving mode other than a finest one of the micro-stepping modes, evaluating, after each speed decrease of the stepper motor, if a second switching condition is fulfilled to permit switching control of the stepper motor into the one of the full-step, half-step, and micro-stepping driving modes having a closest finer step.

7. The method according to claim 6 , wherein evaluating, after each speed decrease of the stepper motor, if the second switching condition is fulfilled comprises said second switching condition including verifying if the remaining computer power is sufficient for allowing switching control of said stepper motor to said one of the full-step, half-step and micro-stepping driving modes having the closest finer step.

8. The method according to claim 7 , wherein verifying if the remaining computing power is sufficient comprises:
evaluating a computing time needed to determine control parameters to be applied to the stepper motor in order for the stepper motor to reach a next position in said current step driving mode;
determining a switching time required by the stepper motor to switch to said next position taking into account the current speed of the stepper motor; and
determining that said remaining computing power is sufficient for allowing switching the stepper motor to said one of the full-step, half-step and micro-stepping driving modes having the closest finer step if said switching time is greater than or equal to said computing time plus a second margin.

9. The method according to claim 8 , wherein determining that said remaining computing power is sufficient further comprises the second margin being greater than a second parameter equal to the difference between the current switching time in said current step driving mode and a next switching time in said driving mode having the closest finer step.

10. The method according to claim 9 , wherein if determining that said remaining computing power is sufficient determines said remaining computer power is not sufficient for allowing switching to said driving mode having the closest finer step, then determining if a difference between a final position and a current position of the motor is smaller than one full step of the current driving mode, and if said final position is not accessible with the current step driving mode, decreasing the speed of the stepper motor for obtaining a sufficient remaining computer power for allowing switching to said one of the full-step, half-step and micro-stepping driving modes having the closest finer step.

11. The method according to claim 10 , wherein controlling said stepper motor comprises controlling motor phases of the stepper motor, and wherein evaluating, after each speed decrease of the stepper motor, if the second switching condition is fulfilled comprises said second switching condition further including a minimum current gap on the motor phases.

12. The method according to claim 11 , further comprising, if said second switching condition is not fulfilled, controlling the stepper motor for a new step in said current step driving mode.

13. The method according to claim 1 , further comprising progressively changing, responsive to the stepper motor running at a constant speed, the current step driving mode until reaching the full step driving mode independent of the remaining computing power.

14. The method according to claim 1 , further comprising progressively changing, in response to the stepper motor running at constant speed, the current step driving mode until reaching a finest one of the micro-stepping modes.

15. A device for driving a stepper motor configured to be driven in step driving modes including a full-step driving mode, a half-step driving mode and micro-stepping modes, and the stepper motor configured to be driven in an acceleration phase, the device comprising a processing unit configured to control a current step driving mode of the motor and, in response to the stepper motor being driven in the acceleration phase and the cu

Assignees

• Stmicroelectronics Grand Ouest Sas

Inventors

• Langouet Emmanuel
• Rousselin Samuel

Classifications

• G06K13/20

  Details · CPC title

• G05B19/40

  Open loop systems, e.g. using stepping motor · CPC title

• H02P8/32

  Reducing overshoot or oscillation, e.g. damping · CPC title

• G05D3/183 Primary

  using stepping motor · CPC title

• H02P8/22 Primary

  Control of step size; Intermediate stepping, e.g. microstepping · CPC title