Robotic Arm Zero Calibration via Forward Kinematics Deviation
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Solution Overview
Problem
Existing calibration methods for robotic arms are difficult to implement due to algorithm complexity, hindering their widespread use in dual-arm collaborative robots that require high precision.
Innovation Solution
A zero calibration method that involves forming a second forward kinematics model by adding zero deviations to each joint of a robotic arm, solving for an end deviation function, and using this function to optimize joint deviations and achieve precise calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the software calibration method using nonlinear equations and Gaussian elimination is used, then the zero calibration accuracy can be improved, but the algorithm implementation complexity increases significantly
Solution Approach 1:
The patent replaces the complex mathematical algorithm system (nonlinear equations and Gaussian elimination) with a simplified computational approach based on forward kinematics modeling. By substituting the intricate algorithm with a more straightforward mathematical model that incorporates zero deviations directly, the implementation complexity is reduced while maintaining calibration accuracy.
Solution Approach 2:
The patent introduces zero deviation parameters (Δq) as additional variables in the forward kinematics model. By changing the parameter structure to include these deviation terms explicitly, the calibration process becomes more direct and easier to implement, avoiding the need for complex nonlinear equation solving while achieving the same calibration objective.
2Measurement precision
If hardware calibration with high-precision scales or marks is used, then the zero calibration accuracy is improved, but the manufacturing cost and machining requirements increase
Solution Approach 1:
The patent replaces the hardware-based calibration system (scales or marks requiring high machining accuracy) with a software-based forward kinematics model. This substitution eliminates the need for precision-machined physical components, reducing manufacturing requirements and costs while achieving comparable or superior calibration accuracy through computational methods.
Solution Approach 2:
Instead of using physical scales or marks that must be manufactured with high precision, the patent creates a virtual model (forward kinematics model) that replicates the robotic arm's geometry and kinematics. This virtual copy allows for flexible adjustment of zero deviations without any physical manufacturing, eliminating machining accuracy requirements entirely.
3Measurement precision
If the end of the robotic arm is controlled to touch a fixed theoretical position point in multiple poses for calibration, then the zero calibration accuracy is improved, but the time required for calibration increases
Solution Approach 1:
The patent performs preliminary modeling of the forward kinematics system with zero deviation parameters before actual calibration execution. By pre-establishing the mathematical model and its relationship with joint angles and end position, the actual calibration process requires only simple data collection and computation, significantly reducing the time needed compared to methods that solve nonlinear equations in real-time during calibration.
Data Source
AI summary
A zero calibration method includes: adding, based on a first forward kinematics model of a robotic arm of a robot, zero deviations of each joint to form a second forward kinematics model, and simultaneously solving the second forward kinematics model and the first forward kinematics model to obtain an end deviation function; sending target end pose instructions to the robotic arm in a current zero point situation, and acquiring a spatial deviation of an actual position of an end; inputting position information of each joint angle and the spatial deviation, after each stop of motion of the end, into the end deviation function, and performing phase shifting to obtain an objective optimization function; and solving the objective optimization function to obtain a zero deviation value.