Traction Apparatus Control Method for Over-traction Prevention
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Solution Overview
Problem
Conventional traction apparatuses experience over-traction due to time lag in feedback control, leading to uncomfortable and delayed application of target traction force, especially when dealing with human subjects.
Innovation Solution
A traction force control method involving three steps: eliminating wire slack, continuously winding the wire to a predetermined initial target value, and stopping the drive mechanism when the target traction force is reached based on detected output from a traction force sensor, preventing over-traction and ensuring smooth application of the set traction force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback control is used to detect and control traction force, then the traction force can be controlled to reach the target value, but time lag occurs due to sensor response and feedback circuit delay causing over-traction
Solution Approach 1:
The control system performs preliminary action by predicting the optimal drive stop time in advance based on the relationship between drive amount and traction force. Instead of waiting for feedback after force application, the system calculates beforehand when to stop driving the wire based on expected traction force development, thereby compensating for the inherent time lag in force detection and feedback processing.
Solution Approach 2:
The invention inverts the conventional feedback control approach by determining the drive stop time from the drive amount rather than from the detected traction force. Instead of monitoring force and stopping when target is reached (which causes overshoot due to delay), the system stops the drive mechanism based on pre-calculated drive amount that corresponds to the target traction force, effectively reversing the control logic to eliminate time lag effects.
2Object-affected harmful factors
If traction force is increased gradually in small increments to prevent over-traction, then over-traction is reduced, but it takes longer time to reach the target traction force and the sense of use is uncomfortable
Solution Approach 1:
The control system performs preliminary calculation of the optimal drive stop time based on the target traction force and the relationship between drive amount and traction force. This allows the system to apply traction force continuously and rapidly without incremental increases, while still preventing over-traction by stopping the drive mechanism at the precisely calculated moment before the target force is exceeded.
3Ease of operation
If wire slack is not eliminated before applying traction force, then the wire can be applied directly to the body, but the conversion between traction amount and traction force becomes inaccurate
Solution Approach 1:
The control system performs preliminary action by detecting and eliminating wire slack before the main traction force is applied. The drive mechanism is activated first to take up any slack in the wire, and only after the slack is eliminated does the system proceed to apply the calculated traction force. This preliminary slack elimination ensures accurate conversion between drive amount and traction force while maintaining ease of operation.
Data Source
AI summary
In the traction apparatus, a control circuit has the following traction control process portions. First, a first traction control process portion winds up the slack portion of a wire by a motor to eliminate the slack of the wire connected to a body to be pulled. Next, a second traction control process portion converts a set traction force that is set by an operation portion to a traction amount to calculate a converted value and, by defining a predetermined amount of a traction amount set based on the converted value as an initial target value, continuously winds up the wire by the motor to that target value. Next, a third traction control process portion detects the traction force that is being applied to the body to be pulled by a load cell, calculates a drive stop time of the motor by defining the set traction force as a final target value on the basis of a detected output of the load cell and drives the drive mechanism, and stops the driving of the motor at a point of reaching the drive stop time.