Phase Detector Edge Polarity Adjustment for Displacement Measurement
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Solution Overview
Problem
Existing displacement measuring devices face inefficiencies in power consumption due to prolonged waiting times when sampling phase information from periodic square wave signals, particularly when the first edge is a falling edge, leading to wasteful power usage and potential measurement inaccuracies.
Innovation Solution
A displacement measuring device with a phase detector that includes a sampling signal generator, counter, edge polarity determinator, and adjuster, which synchronizes with a reference signal to adjust count values when the first edge is a falling edge, ensuring consistent sampling and reducing waiting times by adding a predetermined adjustment to the count value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the sampling is performed without distinguishing rising edge and falling edge, then the sampling operation can be simplified, but the correspondence relation between counter value and phase may be shifted causing measurement inaccuracies
Solution Approach 1:
The edge polarity determinator determines whether the current edge is a rising or falling edge before the sampling occurs. This preliminary determination allows the system to set an appropriate offset value in advance, ensuring that the correspondence relation between counter value and phase is maintained regardless of which edge type is encountered during sampling.
2Reliability
If the waiting time for the first rising edge is prolonged, then the sampling can be synchronized with the signal edges, but the power consumption increases due to the extended waiting period
Solution Approach 1:
The system dynamically adapts its waiting behavior based on the edge polarity. Instead of always waiting for a rising edge, the edge polarity determinator identifies whether the current edge is rising or falling, and the offset setter adjusts the sampling timing accordingly. This allows the system to perform sampling during both rising and falling edges, significantly reducing the average waiting time and thus lowering power consumption while maintaining synchronization reliability.
3Loss of time
If the sampling starts from a falling edge, then the waiting time can be reduced, but the phase information extraction may become inconsistent without proper adjustment
Solution Approach 1:
Before sampling occurs, the edge polarity determinator determines whether the current edge is rising or falling. Based on this determination, the offset setter sets an appropriate offset value that compensates for the difference between rising and falling edge sampling. This preliminary adjustment ensures that phase information extraction remains consistent regardless of which edge type is used for sampling.
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 approach reduces power consumption by limiting waiting times to within a half period of the signal, improving power efficiency and ensuring accurate phase information extraction, even when sampling starts from a falling edge, thus enhancing the precision and efficiency of displacement measurements.
Implementation Method 1
A capacitive encoder includes a main scale and a detection head, which is relatively movable to the main scale and detects relative displacement to the main scale. A number of electrodes are disposed on the main scale and the detection head. A periodic capacity change is generated in electrode patterns according to the relative displacement between the main scale and detection head.
Data Source
AI summary
A phase detector includes a sampling signal generator configured to generate a sampling signal at an edge of a scale signal, a counter configured to count up a count value according to a clock pulse every certain time and to output the count value at a timing instructed by the sampling signal, an edge polarity determinator configured to determine whether an edge polarity of the scale signal is a rising edge or a falling edge and to generate an adjustment signal when the polarity of the edge where the sampling signal is generated is a falling edge and an adjuster configured to add a predetermined adjustment amount to the count value output from the counter when receiving the adjustment signal.