Cargo Crane Straight-Line Trajectory for Suspended-Cargo Swing Prevention
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Solution Overview
Problem
Existing cargo crane systems require complex control methods and additional sensors to prevent cargo swing during conveyance, leading to increased costs and constraints in operation.
Innovation Solution
A cargo crane system that calculates and controls a straight-line trajectory for cargo conveyance using an arm turning mechanism, arm luffing mechanism, and arm extension/contraction mechanism, eliminating the need for feedback control and additional sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If arc-shaped conveyance trajectory is used with conventional swing prevention control, then cargo swing control in circumferential direction is achieved, but cargo swing control in turning radius direction becomes necessary and conveyance time must be adjusted to integral multiple of swing cycle
Solution Approach 1:
Instead of following the conventional arc-shaped trajectory determined by crane arm rotation, the patent inverts the approach by controlling the crane arm to follow a straight-line trajectory in the horizontal plane. This is achieved by coordinating the arm turning mechanism, arm luffing mechanism, and arm extension/contraction mechanism to move the cargo along a straight path rather than an arc, fundamentally changing the motion paradigm to eliminate the need for swing control in the turning radius direction.
Solution Approach 2:
The patent changes the motion parameters by calculating specific turning angles, luffing angles, and arm length variations at each moment to maintain a straight-line trajectory. By dynamically adjusting these parameters based on the desired straight path rather than a fixed arc, the system achieves swing prevention without requiring the conveyance time to be an integral multiple of the swing cycle.
2Measurement precision
If feedback control with sensors is used for swing prevention, then cargo position and speed control is improved, but introduction cost of sensors and additional control devices increases
Solution Approach 1:
The patent employs self-service by using the crane's own motion control mechanisms (arm turning, arm luffing, and arm extension/contraction mechanisms) to inherently prevent cargo swing through precise trajectory control. The system calculates and executes the appropriate motion commands based on the straight-line trajectory requirement, eliminating the need for external sensors and feedback control devices to detect cargo position and speed.
Solution Approach 2:
The patent replaces the sensor-based feedback control system with a mechanical control approach where the crane's motion mechanisms directly enforce the straight-line trajectory. Instead of using sensors to detect swing and then correcting it through feedback, the system mechanically prevents swing by controlling the trajectory at its source through coordinated actuation of the turning, luffing, and extension mechanisms.
3Reliability
If conventional arc trajectory control is used, then cargo swing control in circumferential direction is achieved, but constraint conditions on conveyance time and rope length adjustment are generated
Solution Approach 1:
The patent inverts the conventional approach by not accepting the arc trajectory as fixed, but rather by imposing a straight-line trajectory constraint on the crane's motion. This inversion removes the constraint that conveyance time must be an integral multiple of the swing cycle, as the straight-line path allows flexible timing while inherently preventing swing in the turning radius direction.
Solution Approach 2:
The patent introduces dynamics by continuously adjusting the turning angle, luffing angle, and arm length in real-time to maintain the straight-line trajectory. This dynamic control approach allows the system to adapt to different cargo positions and conveyance requirements without being constrained by fixed swing cycle multiples or rope length adjustments, enhancing operational flexibility.
Data Source
AI summary
A cargo crane including an arm turning mechanism that turns a crane arm; an arm luffing mechanism that adjusts the luffing angle; an arm extension and contraction mechanism that adjusts the arm length; and a control device that calculates a trajectory in which a suspended cargo is conveyed, and that controls the mechanisms. The control device calculates the trajectory so as to be a straight line trajectory as viewed from at least the vertical direction; calculates a turning angle θ, a luffing angle φ, and an arm length L so as to cause the trajectory to be the straight line trajectory by using the cargo start position, the cargo target position, a maximum speed vmax, a suspended cargo swing cycle T, and a start-up time T1; and controls the mechanisms so as to achieve the calculated turning angle θ, luffing angle φ, and arm length L.