DSP-FPGA Motor Control for Three-Motor Field-Oriented Control
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Solution Overview
Problem
Current digital signal processors (DSPs) are limited in their ability to control three-phase brushless motors due to computational intensity and output limitations, making it difficult to achieve field-oriented control and miniaturization in electromechanical devices.
Innovation Solution
A controller system utilizing a digital signal processor (DSP) and a field programmable gate array (FPGA) separates digital control and processing from motor driving signals, allowing for efficient field-oriented control of three brushless motors by distributing tasks between the DSP and FPGA, enabling miniaturization and high-bandwidth torque control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single DSP is used to control three brushless motors with FOC, then device complexity is reduced, but the DSP exceeds its computational capacity and output limitations
Solution Approach 1:
The controller is segmented into two distinct processing units: a DSP for high-level control algorithms and FOC computations, and an FPGA for real-time PWM signal generation and motor phase control. This segmentation divides the computational workload to match each component's strengths, resolving the overload issue while maintaining a unified controller structure.
Solution Approach 2:
The FPGA acts as an intermediary between the DSP and the motor drivers. It receives control commands from the DSP and translates them into precise PWM signals for motor control, effectively mediating the computational tasks and expanding the system's output capabilities beyond what a single DSP could provide.
2Productivity
If multiple DSPs are used to control three brushless motors, then computational capacity is sufficient, but miniaturization is compromised
Solution Approach 1:
The DSP and FPGA are merged into a single integrated controller unit, combining the computational power of multiple processing functions into one compact device. This merging achieves sufficient computational capacity for three motors while maintaining a small form factor that enables miniaturization.
Solution Approach 2:
The FPGA provides multi-functional capabilities, handling both PWM generation and real-time motor control tasks that would otherwise require separate dedicated circuits or additional DSPs. This universality consolidates multiple functions into a single component, reducing overall controller volume.
3Manufacturing precision
If FOC is implemented for three motors, then control precision is improved, but the number of required PWM output signals exceeds DSP capabilities
Solution Approach 1:
The FPGA serves as an intermediary that receives simplified control commands from the DSP and generates the complex PWM signal patterns required for three-phase brushless motor control. This intermediary approach maintains precise control while reducing the complexity of the DSP's output signal requirements.
Solution Approach 2:
The system replaces the need for the DSP to directly generate all PWM signals with an FPGA-based digital logic system. This substitution uses programmable logic to handle the complex signal generation, freeing the DSP to focus on control algorithms and reducing the overall signal generation complexity.
Data Source
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AI summary
Control (10) of a plurality of electronically commutated motors (12) is effected using a control unit and a power unit. The power unit (20, 28) 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 (22), 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.