Lifting Desk Obstacle Detection Using Motor Current Change Rate
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Solution Overview
Problem
Existing lifting desk control methods face challenges in detecting obstacles with high sensitivity and low cost, as they often rely on sensitive but costly sensors or methods that are prone to misjudgment, especially when encountering obstacles with smaller resistance forces.
Innovation Solution
A control method for lifting desks that calculates the current change rate over a set time interval, using a motor, motor drive unit, and arithmetic unit to detect obstacles by comparing the change rate with a set value, eliminating the need for additional sensors and reducing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If mechanical sensors such as piezoelectric sensors or springs are used to detect obstacles, then detection sensitivity is improved, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent replaces mechanical sensors (piezoelectric sensors, springs) with an electrical current detection system. The motor drive unit monitors current changes during lifting operation, and when a specific current threshold is exceeded, an obstacle is detected and the lifting operation is stopped or reversed. This substitution eliminates complex mechanical sensor mounting while achieving reliable obstacle detection.
2Measurement precision
If three-axis acceleration sensors are used to detect obstacles, then obstacle detection capability is improved, but cost increases and misjudgement occurs
Solution Approach 1:
The patent replaces expensive three-axis acceleration sensors with a simple current monitoring system. The motor drive unit continuously monitors the current consumed by the lifting motor, and when the current exceeds a predetermined threshold, an obstacle is detected. This approach eliminates the need for costly acceleration sensors while avoiding misjudgement issues through direct electrical measurement.
Solution Approach 2:
The motor drive unit performs dual functions: it controls the lifting motor operation and simultaneously monitors for obstacles through current detection. This self-service approach eliminates the need for separate detection sensors, reducing system complexity and cost while maintaining reliable obstacle detection capability.
3Ease of manufacture
If abrupt current change detection is used to detect obstacles, then implementation simplicity is improved, but detection sensitivity for small resistance forces deteriorates
Solution Approach 1:
The patent employs dynamic current threshold adjustment based on lifting stage. During different phases of lifting operation (starting, mid-lift, near completion), different current thresholds are applied. This dynamic approach enables the system to detect small resistance forces at appropriate lifting stages while maintaining implementation simplicity through programmable threshold comparison in the motor drive unit.
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 method provides accurate obstacle detection with high sensitivity, avoiding false alarms and misjudgments by focusing on current change rate rather than absolute current values, ensuring safe operation without the need for additional sensors, thus enhancing product safety and reducing costs.
Implementation Method 1
detecting a current of the motor at current time t1 and the current at time t2 after the current time by the current detection unit
Data Source
Figure 1
AI summary
The invention provides a lifting desk control method including a motor drive unit, a current detection unit and an arithmetic unit. The control method comprises the steps of: step 1: detecting current a at the current time t1 and current b at time t2 after the current time by the current detection unit at a set time interval during normal operation, wherein the time t2 is later than the time t1; step 2: calculating the current change value from t2 to t1 and the current change rate L=(b-a)/(t2-tl) by the arithmetic unit; and step 3: comparing the current change rate L with a set value, judging that an obstacle is encountered if the set value is exceeded, and issuing a stopping or retreating instruction to a motor by the motor drive unit. The scheme employed by the invention is to calculate the change rate of current, without the need to consider the magnitude of a current value during normal operation and the influence of the current operating conditions on the normal operating current, so judgment is made with higher accuracy; and the change speed of current is detected and hence protection is not required when the current rises to a set value, so whether an obstacle is encountered is judged with high sensitivity.