Motor Inverter Control Dithering for Low-Resolution Jitter Reduction
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Solution Overview
Problem
Control systems for machines face limitations due to low resolution feedback and inverter components, leading to position and velocity jitter and high-frequency harmonic noise, which are exacerbated by PWM quantization errors, especially at higher frequencies.
Innovation Solution
The implementation of dithering techniques in control circuitry to modify control signals, allowing for improved resolution and reduced jitter by adding a dithering signal to control outputs, effectively addressing quantization errors and noise issues without requiring hardware redesign or high-resolution components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If PWM frequency is increased to reduce high frequency noise, then noise reduction is achieved, but duty cycle quantization error increases
Solution Approach 1:
The patent introduces dithering as an intermediary signal that modulates the PWM duty cycle. This dithering signal acts as a mediator between the control signal and the PWM quantization process, distributing quantization errors across multiple PWM cycles and reducing their impact on position and velocity control precision.
Solution Approach 2:
The patent applies periodic dithering signals to modulate the PWM duty cycle in a periodic manner. This periodic modulation allows the system to explore multiple duty cycle values over time, effectively averaging out quantization errors and improving control resolution without requiring higher PWM frequencies.
2Device complexity
If low resolution feedback components are used to reduce system complexity and cost, then system complexity and cost are reduced, but position and velocity control precision deteriorates
Solution Approach 1:
The patent replaces hardware-based high-resolution feedback components with a software-based dithering and filtering approach. Instead of using expensive high-resolution encoders or feedback sensors, the system uses digital signal processing techniques (dithering combined with moving average filtering) to achieve high-resolution position and velocity control from low-resolution feedback.
Solution Approach 2:
The patent changes the temporal parameters of the control signal by applying dithering that varies the duty cycle over time. This time-domain parameter modification allows the system to extract higher resolution information from low-resolution feedback samples, effectively transforming the resolution limitation from a hardware constraint to a processable signal characteristic.
3Device complexity
If low resolution inverter components are used to reduce system complexity and cost, then system complexity and cost are reduced, but position and velocity control precision deteriorates
Solution Approach 1:
The patent introduces dithering as an intermediary modulation technique between the control algorithm and the low-resolution inverter. This dithering signal mediates the interaction between the control system and the quantized inverter output, allowing the system to achieve finer effective resolution through temporal modulation rather than requiring higher-resolution inverter hardware.
Data Source
AI summary
In described examples of methods and control systems to control a position and/or velocity of a machine, control circuitry is coupled to receive and dither a control signal, and to compute a control output value according to the dithered control signal and a control function. An inverter is coupled to the control circuitry, to control the position and/or velocity according to the control output value.