Load Drive System Power-Line Communication Timing Control
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Solution Overview
Problem
Existing power-line communication systems for vehicles face challenges in reducing the number of wires needed, as intermittent power supply methods increase costs and continuous power supply methods lead to communication interruptions and reduced efficiency due to transition currents from actuator switching.
Innovation Solution
A load drive system with a control unit that adjusts the timing of actuator switching based on the width of the transition period of the power-line current, ensuring the transition occurs outside the communication symbol period, allowing continuous power supply without disrupting communication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If power feeding is divided into communication phase and power feed phase, then communication errors caused by power feeding noise are prevented, but the slave station requires a large-capacity capacitor for power storage, increasing cost
Solution Approach 1:
The patent applies periodic action by dividing the power line usage into distinct time phases: a power feed phase for supplying power to actuators and a communication phase for data transmission. This time-division multiplexing ensures that communication occurs during periods when actuator switching and associated noise are minimized, thereby preventing communication errors without requiring large-capacity capacitors for power storage.
2Use of energy by moving object
If power feed and communication period are not divided, then actuators are continuously fed with power, but communication is interrupted every time an actuator is switched by PWM control, lowering effective communication speed
Solution Approach 1:
The patent implements periodic action by establishing alternating power feed phases and communication phases. During power feed phases, actuators receive continuous power for operation. During communication phases, the system dedicates the power line exclusively to data transmission, avoiding interruptions from actuator switching. This periodic structure maintains both power continuity for actuators and uninterrupted communication windows, thereby preserving communication speed.
3Loss of time
If all sensors and actuators are required to complete control and communication within a desired time period, then the number of actuators and sensors couplable to the same power line is reduced
Solution Approach 1:
The patent uses periodic action to create dedicated communication phases where multiple slave stations can sequentially transmit data without interfering with actuator control timelines. Each slave station is allocated a time slot within the periodic communication phase, allowing multiple devices to share the power line for communication while maintaining their respective control time requirements. This increases the number of devices that can be coupled to the same power line.
4Device complexity
If the number of wires is reduced by power-line communication, then wire consolidation is achieved, but transition currents from actuator switching cause communication errors
Solution Approach 1:
The patent applies periodic action by implementing time-division multiplexing where communication occurs during dedicated communication phases separated from power feed phases. This timing separation ensures that communication takes place when actuator switching and associated transition currents are minimized or absent, thereby preventing communication errors while maintaining the wire-reduction benefit of power-line communication.
Solution Approach 2:
The patent extracts the communication function from the continuous power line signal by creating separate communication phases. During these extracted communication windows, the power line is dedicated solely to data transmission, isolating communication from the harmful effects of actuator switching and transition currents that occur during power feed phases.
Data Source
AI summary
A load drive system for driving a load supplied with power from a power line includes a control unit which controls switching between the power line and the load and a communication unit which communicates using voltage and current of the power line. When performing the switching, the control unit controls, based on a width of a transition period of the power-line current, the transition period being attributable to the switching, timing of the switching so as to move the transition period away from a center of a period corresponding to a symbol communicated by the communication unit.