Hardware PWM Duty Cycle Control for Electric Motor Brake Systems
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Solution Overview
Problem
Existing systems for electric motor vehicle brake systems fail to effectively limit peak currents and current edges, leading to malfunctions and safety/comfort issues due to high computing load and communication limitations between microcontrollers and hardware logic, especially with increasing demands for brake assistance functions and resource constraints.
Innovation Solution
A method and circuit arrangement that dynamically change the PWM duty cycle using a hardware module's logic registers, allowing for rapid adjustments in duty cycle changes independent of the microcontroller, utilizing a slope value to manage current peaks and edges, thereby reducing the load on the vehicle electrical system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the PWM control frequency is increased to improve current peak tracking, then the current peak limitation improves, but the microcontroller computing load increases and other functions cannot be executed
Solution Approach 1:
The patent extracts the PWM duty cycle control function from the microcontroller software and implements it in hardware logic. The hardware module independently adjusts the PWM duty cycle based on stored slope values, removing the computational burden from the microcontroller while maintaining precise current peak tracking capability.
Solution Approach 2:
The hardware logic module autonomously performs duty cycle adjustments using pre-stored slope values without requiring microcontroller intervention. The system serves itself by having the hardware logic independently manage the PWM control, freeing the microcontroller for other brake assistance functions.
2Speed
If the duty cycle change speed is increased to limit current edges faster, then the current edge gradient control improves, but the communication interface bandwidth is exceeded
Solution Approach 1:
The patent prepares slope values in advance and stores them in the hardware logic module before they are needed. These pre-calculated values enable rapid duty cycle changes without requiring real-time communication with the microcontroller, thus avoiding communication interface bottlenecks during critical current edge control moments.
Solution Approach 2:
The patent replaces the software-based duty cycle adjustment mechanism with a hardware logic-based system. This substitution eliminates the need for continuous software-hardware communication during duty cycle changes, enabling faster response times without overwhelming the communication interface.
3Adaptability or versatility
If the microcontroller is used for multiple brake assistance functions, then the system functionality increases, but the computing resources are insufficient for both high-frequency PWM control and other functions
Solution Approach 1:
The patent segments the control system into two independent parts: the microcontroller handles high-level brake assistance function decisions, while the hardware logic module handles low-level PWM duty cycle adjustments. This segmentation allows both multiple brake assistance functions and precise current control to operate simultaneously without resource conflicts.
Solution Approach 2:
The hardware logic module acts as an intermediary between the microcontroller and the PWM control system. It receives minimal control parameters from the microcontroller and autonomously performs the computationally intensive duty cycle adjustments, enabling the microcontroller to support multiple brake assistance functions while maintaining precise current control.
4Manufacturing precision
If the PWM start-up phase duration is extended to reduce current peaks, then the current peak limitation improves, but the motor response time increases
Solution Approach 1:
The patent implements dynamic duty cycle adjustment using hardware logic that can rapidly change the PWM duty cycle according to pre-stored slope values. This dynamic control achieves smooth current rise without extending the start-up phase duration, as the hardware logic can execute adjustments much faster than software-based approaches.
Solution Approach 2:
The patent changes the PWM duty cycle parameter dynamically during the start-up phase using hardware-controlled increments based on slope values. This approach achieves current peak limitation by controlling the rate of change of the duty cycle parameter, while the hardware implementation ensures this occurs rapidly without significant delay to motor response.
Data Source
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AI summary
Method for limiting peak currents, particularly depending on a charge quantity provided by a voltage source, and the maximum pitch of the current flanks of an electric motor (11) for an electrohydraulic motor vehicle brake system, particularly a pump motor, controlled by means of pulse width modulation (PWM), wherein a change to an actual duty cycle (OUT3) of the PWM is made by a first duty cycle of the PWM on a second duty cycle at runtime, characterised in that the change takes place according to a positive or negative pitch value (SLP) calculated and/or changeable at runtime. The invention further describes an electronic circuit arrangement for the implementation of a method for limiting peak currents and the maximum pitch of current flanks.