Manipulator Control Switching Rigid to Flexible Mode
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Solution Overview
Problem
Industrial robots face challenges in automating the joining of components due to positional tolerances of workpieces, with existing solutions like force sensors and dynamic models being underutilized due to practical implementation issues.
Innovation Solution
A method that detects contact forces between a manipulator and a workpiece using actual driving forces and a dynamic model, allowing for a switch from rigid to flexible control to prevent damage during joining, using force-based impedance control and monitoring of contact forces to ensure correct joining.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rigid position control is used to approach workpiece poses quickly, then productivity is improved, but the risk of damaging the workpiece or manipulator upon contact increases
Solution Approach 1:
The control system dynamically switches between rigid position control and flexible impedance control based on contact detection. During approach, rigid control enables fast positioning; upon contact detection through driving force analysis, the system transitions to flexible control that allows compliant interaction, preventing damage while maintaining productivity
Solution Approach 2:
The system changes control parameters by detecting contact forces through comparison of actual and model driving forces. When contact is detected, control parameters are adjusted to switch from position-controlled rigid mode to force-controlled flexible mode, enabling safe contact interaction
2Measurement precision
If additional force sensors are installed to detect contact forces, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The manipulator uses its own drive system to detect contact forces. By analyzing the driving forces already present in the drive system and comparing them with a dynamic model, the system self-detects contact forces without requiring additional force sensors, thus avoiding increased device complexity
Solution Approach 2:
The patent replaces mechanical force sensors with a computational approach. Instead of using physical sensors to measure contact forces, the system uses a dynamic model to calculate expected driving forces and compares them with actual driving forces, substituting mechanical measurement with mathematical modeling and analysis
3Object-affected harmful factors
If flexible control is used during workpiece handling, then damage risk is reduced, but productivity decreases due to slower response
Solution Approach 1:
The control mode dynamically adapts to the operational phase: rigid control during approach for speed, flexible control during contact for safety. This dynamic switching resolves the contradiction by applying the appropriate control characteristic at the appropriate time
Solution Approach 2:
The system rushes through the approach phase using rigid control to minimize cycle time, then quickly transitions to flexible control only when contact is detected. This skipping of prolonged flexible control maintains productivity while ensuring safety when needed
Data Source
Figure 1~2
Figure 3A~3C
Figure 4A~4D
AI summary
A method according to the invention for controlling a manipulator, in particular a robot, comprises the step of: detecting a contact force between the manipulator and a workpiece (2; 20) based on actual drive forces (t) and drive forces (tModel) of a dynamic model (M d2q/dt2 + h(q, dq/dt) = tModel) of the manipulator; and at least one of the steps of: a) multi-stage measurement of a position of the workpiece (2) based on detected contact forces (S40, S70), in particular with the steps of: determining positions of non-aligned contours, in particular edges (2.1, 2.2), of the workpiece (2) by detecting poses of the manipulator and the contact forces (S40) acting on it; approaching reference points of the workpiece (2), in particular defined by recesses (3.1, 3.2, 3.3), based on contours (2.1, 2.2) detected in this way.2) of the workpiece (S50); and determining the positions of these reference points by detecting contact forces acting on the manipulator during movement (S70); and/or b) joining a workpiece (4; 40) under compliant control (S130; S230), wherein a joining state of the workpiece is monitored based on a detected contact force and/or an end pose of the manipulator reached under compliant control, in particular with the steps: holding the workpiece with the manipulator in at least two force contacts (1.1, 1.2); positioning the workpiece in a joining basic position (Fig. 3A); moving the workpiece to a joining end position (Fig. 3B) by releasing at least one force contact (1.2); and/or c) rigidly controlled approach to a pose (S10; S110; S210); as well as switching to a compliant control based on a detected contact force (S30; S130; S230).