Method and circuit arrangement for controlling a stepper motor
AssigneeAnalog Devices International Unlimited Company
InventorBernhard Karl-Heinz Dwersteg
Life of this patent
Estimating the term…
Abstract
A new method and circuit arrangement for operating a stepper motor in a voltage-based operating mode with a control loop over the whole operating range of speeds of a stepper motor. The method/circuit arrangement includes calculating a load angle of the stepper motor. The load angle is then used to calculate a voltage-based control signal suitable for operating a known motor driver circuit, such as a chopper, to drive the stepper motor coils. This enables improved control over the stepper motor which can improve control stability.
Claims20
A method of operating a stepper motor in a voltage-based operating mode with a control loop, the stepper motor comprising at least a first motor coil and a second motor coil, the method comprising:
- measuring a first motor coil current from the first stepper motor coil;
- measuring a second motor coil current from the second stepper motor coil;
- determining a coil current vector based on:
- the first motor coil current;
- and the second motor coil current, wherein there is a predetermined phase angle relationship between the first motor coil current and the second motor coil current;
- determining a coil current phase angle between the coil current vector and a pre-defined reference angle;
- receiving a first voltage-based control signal for operating the stepper motor;
- calculating a load angle of the stepper motor based on:
- the coil current phase angle;
- an absolute value of the coil current vector;
- and
- the first voltage-based control signal;
- calculating a second voltage-based control signal based on the load angle;
- and
- operating the stepper motor using the second voltage-based control signal.
A circuit arrangement for operating a stepper motor in a voltage-based operating mode with a control loop, the stepper motor comprising at least a first motor coil and a second motor coil, the circuit comprising:
- a control unit for a voltage-based operating mode, configured to generate:
- a first voltage-based control signal for operating the stepper motor at a first time;
- a second voltage-based control signal for operating the stepper motor at a second time, wherein the first time proceeds the second time at which the stepper motor is operated;
- an analog-to-digital converter configured to:
- measure a first motor coil current from the first stepper motor coil;
- measure a second motor coil current from the second stepper motor coil, wherein a coil current vector is based on:
- the first motor coil current;
- and the second motor coil current, wherein there is a predetermined phase angle relationship between the first motor coil current and the second motor coil current, wherein a coil current phase angle is an angle between the coil current vector and a pre-defined reference angle;
- a load angle calculation unit configured to calculate the load angle of the stepper motor based on:
- the coil current phase angle;
- an absolute value of the coil current vector;
- and
- the first voltage-based control signal;
- wherein the second voltage-based control signal is based on the load angle of the stepper motor.
A method for damping stepper motor resonances of a stepper motor, the stepper motor comprising at least a first motor coil and a second motor coil, the method comprising:
- measuring a first motor coil current from the first stepper motor coil;
- measuring a second motor coil current from the second stepper motor coil;
- determining a coil current vector based on:
- the first motor coil current;
- and the second motor coil current, wherein there is a predetermined phase angle relationship between the first motor coil current and the second motor coil current;
- determining a coil current phase angle between the coil current vector and a pre-defined reference angle;
- generating a micro-step sequencer waveform for operating the stepper motor in a micro-step mode of operation, wherein the micro-step sequencer waveform is discrete and comprises at least:
- a first micro-step value associated with a first phase angle position of a micro-step sequencer waveform;
- and a second micro-step value associated with a second phase angle position of the micro-step sequencer waveform;
- adjusting the second phase angle position relative to the first phase angle position based on the coil current phase;
- and,
- generating the second voltage-based control signal based on the second phase angle position.
Dependencies are inferred from the claim text.