Watchdog Timer Segmentation for Motor Control Safety
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Solution Overview
Problem
Existing image forming apparatuses face issues where the motor continues to operate due to the inability to detect CPU abnormalities when the watchdog timer's function is stopped by the CPU, leading to potential unsafe conditions and increased power consumption.
Innovation Solution
An information processing apparatus is designed with a first control unit that outputs commands for driving an electric part, a detection unit to identify abnormalities in the first control unit, and a second control unit that manages the supply of drive signals. The second control unit cuts off the drive signal when an abnormality is detected or when instructed to stop the detection process by the first control unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the watchdog timer function is stopped by the CPU to enable power saving or normal operation, then power consumption is reduced and normal operation is enabled, but the ability to detect CPU abnormalities is lost
Solution Approach 1:
The patent divides the control system into three independent components: the CPU (first control unit), the watchdog timer (detection unit), and the motor controller (second control unit). This segmentation allows the watchdog timer to operate independently of the CPU, enabling it to detect CPU abnormalities even when the CPU is in sleep mode or has stopped the watchdog timer function. The independent architecture ensures that power saving operations do not compromise safety monitoring.
Solution Approach 2:
The patent introduces an intermediary mechanism where the motor controller receives dual control signals: one from the CPU for normal operation and another from the watchdog timer for safety monitoring. The motor controller integrates these signals to control motor operation, ensuring that the motor can be stopped based on watchdog timer detection even when the CPU is abnormal or in sleep mode. This intermediary approach enables independent safety monitoring without affecting normal operation.
2Use of energy by moving object
If the CPU stops the watchdog timer function for power saving during sleep mode, then energy efficiency is improved, but the motor may continue to operate due to undetected CPU abnormalities
Solution Approach 1:
The patent segments the control functions so that the watchdog timer operates independently from the CPU. This allows the watchdog timer to continue monitoring CPU status even when the CPU enters sleep mode or stops the watchdog timer function for power saving. The independent watchdog timer can detect CPU abnormalities and trigger motor shutdown without requiring continuous CPU operation, thus preventing harmful motor operation while maintaining energy efficiency.
Solution Approach 2:
The patent implements preliminary action by having the watchdog timer pre-configured to automatically trigger motor shutdown when CPU abnormalities are detected. The motor controller is pre-programmed to receive and act on watchdog timer signals. This preliminary setup ensures that when CPU abnormalities occur during sleep mode, the system can automatically respond by stopping the motor without requiring continuous CPU intervention, thus preventing unsafe operation while maintaining power saving benefits.
3Reliability
If the watchdog timer is made independent of CPU control for reliable abnormality detection, then detection reliability is improved, but device complexity increases
Solution Approach 1:
The patent applies multi-functionality to the motor controller, which serves dual purposes: receiving normal operation commands from the CPU and receiving safety shutdown commands from the watchdog timer. This universal approach allows a single component (motor controller) to handle both normal control and safety monitoring functions, reducing the need for additional separate components. The watchdog timer maintains independent monitoring capability while the motor controller integrates both control signals, achieving reliable detection without proportionally increasing overall system complexity.
Data Source
AI summary
An information processing apparatus includes a first control unit that outputs a command for driving an electric part, a detection unit that detects an abnormality of the first control unit, and a second control unit that controls whether or not supply of a drive signal based on the command for driving the electric part to the electric part can be performed, in which the first control unit outputs instruction signals for instructing execution and stop of the detection by the detection unit, and the second control unit cuts off the supply of the drive signal to the electric part in a case where the detection unit detects the abnormality of the first control unit and a case where the instruction signal for instructing the stop of the detection by the detection unit is output from the first control unit.