Rotation Control Device for Working Machine Torque Limiting
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Solution Overview
Problem
Conventional swing control systems for working machines, such as hydraulic excavators, face issues with excessive output torque and reverse movement during operations like pressing work or turning on sloping grounds, where feedback control leads to stagnation and potential reverse movement, requiring manual adjustment by operators to prevent wind forces.
Innovation Solution
A swing control system that includes a target torque limitation mechanism, using first and second target torque calculations to limit the output torque of the electric motor, and a third target torque calculation to prevent reverse movement by adjusting the rotation angle, ensuring the system automatically prevents excessive torque and reverse movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If feedback control is used to control output torque to target torque, then the swing speed is controlled according to operation stroke, but the output torque cannot be adjusted during pressing work where rotation speed is 0
Solution Approach 1:
The control system is segmented into multiple target torque calculation means (first, second, third, and fourth target torque calculation means), each responsible for different operating conditions. This allows the system to select appropriate torque control strategies for different work modes, enabling torque adjustment during pressing work while maintaining overall system manageability through modular architecture.
2Reliability
If target torque is increased to prevent reverse movement on sloping ground, then stability is improved, but excessive torque may cause damage or instability
Solution Approach 1:
The control system dynamically adjusts target torque based on detected swing angle and operation state. The fourth target torque calculation means specifically calculates torque for preventing reverse movement when needed, while the target torque limitation means ensures the torque does not exceed safe limits. This dynamic adaptation provides necessary stability on sloping ground while preventing excessive torque damage.
Solution Approach 2:
The swing angle detection means continuously monitors the actual swing angle and feeds this information back to the control system. The fourth target torque calculation means uses this feedback to determine when reverse movement prevention is needed and calculates appropriate torque levels, creating a closed-loop control that maintains reliability without excessive force.
3Extent of automation
If automatic reverse movement prevention is implemented, then operator intervention is reduced, but system complexity increases
Solution Approach 1:
The fourth target torque calculation means is prepared in advance to calculate torque for reverse movement prevention. When the swing angle detection means detects conditions indicating potential reverse movement, the system automatically activates the appropriate torque control without requiring operator intervention. This preliminary preparation enables automatic protection while keeping the control logic integrated and manageable.
Data Source
AI summary
To automatically prevent a reverse movement by inhibiting an excessive increase in an output torque of an electric motor.A means (31) calculates a target value for a rotation speed based on a command from a system (20), a means (32) calculates a deviation between a detection value from a rotation speed sensor (81) and the target value, a means (33) calculates a first target torque in a direction that the deviation will be eliminated, and a means (34) calculates, based on a command from the system (20), a second target torque in the same direction as the target value. A means (50) calculates a variation in a rotation angle of an electric motor (12) in a first range, and a means (60) calculates the same variation in a second range. A means (40) calculates, based on the variations from the means (50, 60), a third target torque in a direction that the rotation angle will return to a rotation angle before a predetermined time (t), and a means (73) limits the first target torque to one of the second and third target torques, said one target torque being in the same direction as the first target torque and being greater in absolute value. Substantially an entirety of the first range specifies a range for the variation in one direction, a remaining small range specifies a range for the variation in the other direction, substantially an entirety of the second range specifies a range for the variation in the other direction, and a remaining small range specifies a range for the variation in the one direction.