Brushed DC Motor Torque Limiting Under Voltage and Current Constraints
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Solution Overview
Problem
Existing methods for controlling brushed DC motors do not effectively address operating constraints such as maximum available voltage, supply current limits, and motor current limits, leading to inefficiencies and potential overloading.
Innovation Solution
A method and system that determines torque limits based on brush voltage drop across the DC motor's brushes, considering motor current and supply voltage constraints, using anti-windup control strategies to ensure the motor operates within these limits, employing a PI control loop with torque and current regulators to manage torque commands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If torque output is increased to improve motor performance, then power delivery is enhanced, but operating constraints such as supply current limits and maximum available voltage are violated
Solution Approach 1:
The patent implements dynamic torque limiting by continuously calculating torque limits based on real-time operating conditions (supply voltage, supply current, motor current) and adjusting the torque command accordingly. This allows the motor to operate at maximum safe torque under varying conditions without violating constraints, resolving the contradiction between maximizing power output and maintaining reliable operation within electrical limits.
2Reliability
If complex control algorithms are used to precisely manage torque limits, then operating constraint satisfaction improves, but computational burden increases
Solution Approach 1:
The patent segments the torque limiting control into distinct computational steps: calculating brush voltage drop, determining supply current limit, determining maximum available voltage, calculating torque limits from these constraints, and applying the minimum torque limit. This structured segmentation simplifies the control algorithm while maintaining precise constraint satisfaction, reducing computational burden compared to monolithic approaches.
Solution Approach 2:
The patent performs preliminary calculations of brush voltage drop and torque limits before applying torque commands. By pre-calculating these parameters based on current operating conditions, the system avoids complex real-time computations during torque application, reducing computational burden while ensuring constraints are satisfied.
Data Source
AI summary
Technical solutions are described for controlling a brushed direct current (DC) motor, including: determining, based on one of a motor current command or an actual motor current, a brush voltage drop across a set of brushes of the brushed DC motor; determining, based on the brush voltage drop, at least one of: a first torque limit based on a supply current value not exceeding a supply current limit, and a second torque limit based on a controller supply voltage value not exceeding a maximum available voltage; determining a final torque limit based on the at least one of the first torque limit and the second torque limit; determining a limited torque command based on a torque command and not to exceed the final torque limit; determining a voltage command based on the limited torque command; and applying a DC voltage to the brushed DC motor based on the voltage command.