Manipulator Path Control for Safe Workpiece Loss in Bending
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Solution Overview
Problem
The challenge in controlling the safe movement of a workpiece, such as a sheet metal part, in a processing area of a bending machine without protective fences is exacerbated by undefined friction conditions and the risk of workpiece loss due to uncertain friction forces and changing center of gravity, which can lead to unintended collisions and loss of control during braking.
Innovation Solution
A method that involves determining the center of gravity of the workpiece, calculating an envelope sphere, and dynamically calculating and controlling the movement path of the holding tool to ensure a controlled loss of the workpiece within a defined danger zone, using sensors and compensation movements to account for friction uncertainties and prevent tilting moments, thereby eliminating the need for protective fences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If safety fences are omitted to enable guard-free operation, then productivity and ease of operation improve, but safety and reliability deteriorate due to uncontrolled workpiece loss and collisions
Solution Approach 1:
The system performs preliminary calculation of the center of gravity and potential impact points before movement, and continuously monitors during operation. This advance preparation and continuous monitoring enable the system to predict and prevent unsafe conditions before they occur, allowing guard-free operation while maintaining safety
Solution Approach 2:
The system continuously calculates the current impact point during workpiece movement and uses this feedback to dynamically adjust the holding tool's movement path. This real-time feedback mechanism ensures that even if workpiece loss occurs, the impact remains within the danger zone, thereby maintaining safety without requiring physical fences
2Device complexity
If conventional holding methods are used with undefined friction conditions, then device complexity is reduced, but reliability deteriorates due to workpiece ejection and loss of control
Solution Approach 1:
The system dynamically changes the movement parameters of the holding tool based on calculated friction forces and workpiece characteristics. By continuously adjusting acceleration, deceleration, and movement path parameters, the system compensates for undefined friction conditions and prevents workpiece ejection, maintaining reliability without increasing holding tool complexity
3Reliability
If dynamic calculation and control of movement path is implemented, then safety and reliability improve, but device complexity and computational requirements increase
Solution Approach 1:
The system uses an intermediary computational model that calculates the relationship between holding tool movement and workpiece impact point. This mathematical intermediary simplifies the control task by providing direct formulas for determining safe movement paths, reducing the complexity of the control system while maintaining high safety standards
4Reliability
If braking distance is minimized to reduce collision risk, then safety improves, but control precision deteriorates due to undefined friction conditions
Solution Approach 1:
The system performs preliminary calculation of braking parameters based on predicted friction conditions and workpiece characteristics before deceleration begins. This advance preparation allows the system to minimize braking distance while maintaining precise control, overcoming the limitation of undefined friction conditions during actual braking
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 enhances safety by ensuring that the workpiece is safely controlled and managed, even under undefined friction conditions, by dynamically adjusting the movement path to prevent collisions and maintain control during potential loss, thus increasing safety and reliability in the processing area.
Implementation Method 1
the workpiece is typically held by a holding tool by applying a holding force to at least one workpiece surface... An undefined frictional force between the holding tool and the workpiece poses a risk
Implementation Method 2
the center of gravity of a workpiece, particularly a sheet metal part, can change during successive forming steps. This can, under certain circumstances, trigger a collision warning within the machine control system, hindering or even preventing a controlled braking process, potentially leading to a machine standstill. In extreme cases, this, in combination with undefined friction conditions, can result in the workpiece being lost from the holding tool
Data Source
Figure 1~2
Figure 3~4
Figure 5~6b
AI summary
The invention relates to a method for controlling the safe movement of a workpiece (1), e.g., in a working area (7) of a bending machine (2) without a safety fence, wherein the workpiece (1), e.g., a sheet metal part, is held by a holding tool (16) of a multi-axis movable manipulator (10) and moved within the working area (7). The object of the invention is to execute the movement of the workpiece in such a way that, in the event of a workpiece loss, the point of impact (18) always lies within the danger zone (8). The point of impact (18) corresponds to the point in the surroundings upon which the workpiece (1) impacts when the workpiece (1) detaches from the holding tool (16) (workpiece loss) and moves freely in space along a trajectory (19). In the method, the workpiece center point (13) is determined, and a sphere (11) is calculated, which is defined by the determined center of gravity (13) of the workpiece and a radius (14) to the point (15) furthest away from the workpiece (1).During the movement of the workpiece (1), the point of impact (18) of the workpiece is continuously calculated and a dynamic calculation and control of a movement path (22) of the holding tool (16) is carried out such that the point of impact (18) of the workpiece (1) in the event of workpiece loss occurs within a danger zone (8) of the machining area (7).