Safety Controller Task Synchronization for Motor Control Delay
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Solution Overview
Problem
The existing control systems for service robots and transportation equipment face challenges in synchronizing motor control instructions with the control cycle due to the delay between the main control ECU and the motor amplifier ECU, affecting safety and efficiency.
Innovation Solution
A safety controller that includes a processor for scheduling safety-related and normal control tasks, a signal generation unit for generating carrier signals, and an interrupt signal generation unit to switch between safety-related and normal control time partitions, ensuring timely updates and synchronization of control content with the control target.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the main control ECU operates at a slower cycle (about 1 msec) to ensure safety and reliability, then the safety and reliability are improved, but the control synchronization with the motor amplifier ECU (operating at about 30 μsec cycle) deteriorates, causing delay in motor control instructions
Solution Approach 1:
The control system is segmented into two independent control loops: a safety control loop operating at 30 μsec cycles and a normal control loop operating at 1 msec cycles. The safety control unit independently processes safety-related commands and controls the motor amplifier, while the normal control unit handles general motor control. This segmentation allows each loop to operate at its optimal speed without interfering with the other, resolving the contradiction between safety reliability and control timing.
2Reliability
If independent safety control and normal control ECUs are used to ensure safety, then the reliability is improved, but the device complexity increases
Solution Approach 1:
The patent merges the safety control unit and normal control unit into a single integrated control device. The control device includes both a safety control unit with safety command generation unit and safety control unit, and a normal control unit with normal command generation unit, all within one ECU. This integration reduces device complexity by eliminating the need for separate independent ECUs while maintaining the reliability benefits of independent control loops through logical separation of functions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables control synchronization with the control cycle while maintaining safety, reducing the delay in motor control instructions and allowing for independent operation of safety-related and normal control tasks, thus enhancing the overall control efficiency and safety.
Implementation Method 1
The motor amplifier ECU generates a PWM (Pulse Width Modulation) signal for controlling the motor, based on the control content indicated by the servo command value output from the main control ECU
Implementation Method 2
an interrupt signal generation unit that generates an interrupt signal to the processor and outputs the interrupt signal to the processor every second predetermined cycle of the carrier signal
Data Source
AI summary
To perform control in synchronization with a control cycle of a control target while maintaining safety. A safety controller includes: a processor; a system program for controlling allocation of an execution time of the processor to tasks; a signal generation unit that generates a periodic carrier signal; a control unit that updates a control content for the control target with a control content instructed by instruction information output from the processor, every first predetermined cycle of the carrier signal, and performs PWM control for the control target; and an interrupt signal generation unit that outputs an interrupt signal to the processor every second predetermined cycle of the carried signal. The processor executes the system program to schedule the tasks in accordance with scheduling information on a safety-related time partition and a normal control time partition, switches the time partitions according to an output of the interrupt signal, and outputs the instruction information to the control unit by a normal control task or a safety-related task.