Robot Load Weight and Center of Gravity from Static Pose Wrenches
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Solution Overview
Problem
Existing methods fail to accurately determine the weight and center of gravity of a load for a robot manipulator, which is crucial for precise handling and movement.
Innovation Solution
A method involving gripping the load, moving it into distinct static poses, determining external wrenches for each pose, and averaging weight and center of gravity estimations across these poses to achieve accurate calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing methods are used to determine weight and center of gravity, then the process is simpler, but the accuracy of determination is insufficient
Solution Approach 1:
The determination process is segmented into multiple distinct static poses (at least three different poses), with each pose providing independent measurement data. By dividing the measurement into separate static configurations, the system achieves more accurate weight and center of gravity determination through multiple data points while maintaining a relatively simple measurement approach for each individual pose.
Solution Approach 2:
The system performs preliminary calibration by moving the load into predetermined static poses before final measurement. These preliminary positioning actions establish known configurations that enable accurate calculation of weight and center of gravity, preparing the system in advance for the actual determination process.
2Productivity
If dynamic measurement is used, then the measurement speed is faster, but dynamic forces and torques interfere with the measurement
Solution Approach 1:
The system uses static poses that are maintained for specific periods of time, allowing static measurement of forces and torques without dynamic interference. By holding each pose statically, the measurement captures only the external wrench components without Coriolis forces, tangential accelerations, or centrifugal forces that would contaminate dynamic measurements.
Solution Approach 2:
The measurement process employs periodic static poses maintained for specific time intervals. Each pose is held long enough to complete accurate force and torque measurements, then the system transitions to the next pose. This periodic static measurement approach eliminates dynamic forces while maintaining measurement productivity through systematic pose transitions.
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 efficiently determines the weight and center of gravity of a load, enabling precise control and movement of the load by the robot manipulator.
Implementation Method 1
The robot manipulator (1) has torque sensors (13) designed to determine torques in the joints (7)
Implementation Method 2
the robot manipulator has strain gauges on the joints or on the links, wherein the strain gauges are each designed to detect tensions in the supporting material of the robot manipulator
Implementation Method 3
gripping the load by the end effector
Data Source
AI summary
A method of determining a weight and a center of gravity of a load for a robot manipulator, the method including: gripping the load using an end effector; moving the load into a number n of distinct static poses; determining an external wrench wrench Fext for each of the n static poses; determining, in a base coordinate system, at least components of each external wrench Fext that indicate the external forces; determining a particular estimation of the weight of the load from a particular component pointing in a direction of a gravity vector from among the components of each external wrench Fext that indicate the external forces in the base coordinate system, and from a magnitude of the gravity vector; determining the weight of the load by averaging respective estimations of the weight of the load; determining estimations of coordinates of the center of gravity of the load for each of the n static poses based on the weight of the load or the particular estimation of the weight of the load determined for a particular static pose and based on the components of the external wrench Fext that indicate externally acting torques; and determining the center of gravity of the load by averaging respective estimations of coordinates of the center of gravity.