Winch Brake Pressure Control During Free-Mode Switching
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Solution Overview
Problem
In cranes with electric pedal systems, the actual brake force on the winch drum becomes instantaneously smaller than the brake force corresponding to the operation amount when the controller automatically switches the brake device from the coupled mode to the free mode.
Innovation Solution
A winch control device with a controller that performs first, second, and third controls to manage the mode switching of the brake device, using a set pressure command to stabilize the brake force, preventing undershoot by adjusting the secondary pressure of the electromagnetic proportional valve.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the controller automatically switches the brake device from coupled mode to free mode using an electric pedal system, then the operator convenience is improved and manual mode switching is eliminated, but the actual brake force on the winch drum becomes instantaneously smaller than the brake force corresponding to the operation amount
Solution Approach 1:
The controller performs preliminary action by setting the secondary pressure to a predetermined value before completing the mode switching from coupled mode to free mode. This ensures that the brake force is already at the appropriate level before the mode transition finishes, preventing the instantaneous reduction of brake force that would otherwise occur during automatic switching.
Solution Approach 2:
The system uses feedback by monitoring the operation amount of the brake operation and adjusting the secondary pressure accordingly. The controller continuously compares the actual brake force with the desired brake force based on operation amount, and modifies the pressure command to the brake force regulator to maintain consistency during mode transitions.
2Speed
If the mode switching valve switches the brake device to free mode immediately, then the response speed is improved, but the brake force becomes unstable and undershoots the required level
Solution Approach 1:
The controller performs preliminary action by pre-adjusting the secondary pressure to a predetermined value before the mode switching valve completes its transition to free mode. This anticipatory pressure adjustment ensures that when the mode switching finishes, the brake force is already stable and at the correct level, avoiding both delay and instability.
Solution Approach 2:
The system applies beforehand cushioning by setting the secondary pressure to a predetermined value that compensates for the expected brake force reduction during mode switching. This preemptive pressure adjustment cushions against the potential undershoot, ensuring smooth and stable brake force transition without oscillation or instability.
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
The solution effectively inhibits the instantaneous reduction of brake force on the winch drum, ensuring consistent brake force application during mode transitions, thereby preventing unintended free fall of the suspended load.
Implementation Method 1
a brake device that generates a brake force on the winch drum
Implementation Method 2
a mode switching valve that switches a mode of the brake device between a coupled mode in which a drive force of the winch motor is capable of being transmitted to the winch drum and a free mode
Implementation Method 3
a brake force regulator that outputs a secondary pressure for adjusting the brake force in the free mode
Data Source
AI summary
A controller of a winch control device performs: a first control for, when a winding operation is applied in a free mode, switching the mode of a brake device from the free mode to a coupled mode; a second control for, when a winch operating member is returned to a neutral position, switching the mode from the coupled mode to the free mode in a state where a command for adjusting the secondary pressure of a brake force regulator to a set pressure, which is larger than an operation amount corresponding pressure corresponding to the operation amount of a brake operation, is input into the brake force regulator; and a third control for inputting into the brake force regulator a command for adjusting the secondary pressure of the brake force regulator to the operation amount corresponding pressure.