Digital motor control unit
Control of a plurality of electronically commutated motors is effected using a control unit and a power unit. The power unit enables the provision of commutation signals to each controlled motor. The control unit comprises a DSP and a FPGA. An input memory of the FPGA is mapped to the DSP. In use, the DSP determines motor repositioning signals, on the basis of a received motor position demand signal describing demanded motor positions and the encoded motor position data, and loads the motor repositioning signals into the input memory of the FPGA. The FPGA is operable to generate motor driving current signals for driving the motors into the demanded motor positions, on the basis of the motor repositioning signals and motor phase current samples collected by the power unit, and to output the motor driving current signals to the power unit.
1. A controller for controlling a plurality of electronically commutated motors, comprising a control unit and a power unit,
the power unit comprising:
a motor phase current sampler operable to provide, to the control unit, motor phase current samples from motor phase currents of the motors;
a motor position encoder operable to provide, to the control unit, encoded motor position data for angular positions of the motors; and
a plurality of drivers, each driver being operable to generate commutation signals, on the basis of respective motor driving current signals,
the control unit comprising:
a digital signal processor, DSP, and
a field programmable gate array, FPGA, having an input memory mapped to the DSP,
the DSP being operable to determine motor repositioning signals, on the basis of a received motor position demand signal describing demanded motor positions and the encoded motor position data, and to load the motor repositioning signals into the input memory of the FPGA, and
the FPGA being operable to execute a current control algorithm by converting the motor repositioning signals generated by the DSP into information from which motor driving current signals can be derived and generate motor driving current signals for driving said motors into said demanded motor positions, on the basis of the motor repositioning signals and the motor phase current samples, and to output said motor driving current signals to the power unit.
2. A controller in accordance with claim 1 wherein the DSP further comprises an analogue to digital converter, ADC, operable to convert said motor phase current samples into motor phase current measurements, and to load said motor phase current measurements into said input of said FPGA, and wherein said FPGA is operable to generate said motor driving current signals further on the basis of the motor phase current measurements.
3. A controller in accordance with claim 1 wherein the DSP comprises a position loop counter operable to determine a processing speed for the determining of motor positioning signals, and wherein the FPGA comprises a clock operable to determine a processing speed for the determining of motor driving current signals, the processing speed for the FPGA being greater than the processing speed for the DSP.
4. A controller in accordance with claim 3 wherein the processing speed for the FPGA is at least 5 times greater than the processing speed for the DSP.
5. A controller in accordance with claim 1 wherein the FPGA is operable to establish a respective process for the generation of motor driving current signals for each controlled motor, the FPGA further comprising a state machine operable to switch between processes per motor.
6. A controller in accordance with claim 5 wherein the FPGA defines a current signal processing unit, and wherein, in use, the current signal processing unit is utilised, sequentially, by the state machine in respect of each controlled motor.
7. A controller in accordance with claim 1 wherein the power unit comprises a power supply regulator operable to receive a power supply from a source of electrical power and to present, to the control unit, a regulated power supply.
8. A method of controlling a plurality of electronically commutated motors, comprising a control process and a power process;
the power process comprising:
providing, to the control process, motor phase current samples from motor phase currents of the motors;
providing, to the control process, encoded motor position data for angular positions of the motors; and
generating, for each controlled motor, commutation signals, on the basis of respective motor driving current signals,
the control process comprising:
mapping an input memory of a field programmable gate array, FPGA, to a digital signal processor, DSP,
determining, by the DSP, motor repositioning signals, on the basis of a received motor position demand signal describing demanded motor positions and the encoded motor position data, and loading the motor repositioning signals into the input memory of the FPGA, and
executing, by the FPGA a current control algorithm by converting the motor repositioning signals generated by the DSP into information from which motor driving current signals can be derived, and generating motor driving current signals to drive the motors into the demanded motor positions, on the basis of the motor repositioning signals and the motor phase current samples, and outputting the motor driving current signals to the power process.