Mechanical arm safety collision strategy based on external force observer

Abstract

The invention discloses a mechanical arm safety collision strategy based on an external force observer. The mechanical arm safety collision strategy comprises the steps that firstly, a dynamic model of a flexible joint mechanical arm under external force interference is established and the stress is analyzed; a double encoder method is adopted to collect the angle information of the motor end andthe connecting rod end, and the external force observer needs to measure the joint position and speed and does not need to detect the acceleration q-diaeresis or an inverse matrix of an inertial matrix, so as to reflect the current input; and for a multi-degree of freedom mechanical arm, the computation of generalized momentum p and vector eta requires recursion or iteration methods, the observercan detect external torque or force, a dynamic threshold value is set according to the observation value of the observer, when the observed value exceeds the limit range of the dynamic threshold value, a control system considers that collision occurs, a touch stop mode is immediately switched to guarantee the safety of the operator and robots, and the safety responses at different motion speeds are achieved.

Description

technical field [0001] The invention belongs to the field of industrial robot control, and specifically relates to a safety collision strategy of a mechanical arm based on an external force observer. The collision strategy does not rely on external sensors to realize collision detection between a robot and an obstacle, and does not use visual detection of the position of the obstacle. , but adopts the method of detecting external force based on the external force observer based on generalized momentum, so as to realize the safe response under different motion speeds. Background technique [0002] Safety is the primary problem to be solved to achieve "human-machine integration". When the robot operates in an unstructured environment, the safety problem is the primary concern. According to the application environment and functional requirements of the robot, its safety can be divided into two categories: Classes: Self-Security and Interaction-Security. In fact, human-machine ...

AI Technical Summary

Problems solved by technology

Some manipulators use joint force sensors, and install torque sensors on each joint. It can be inferred whether the manipulator has collided with the observed value of the joint torque; Sensitive skin detects the external force collision of the robot's whole body, and the sensitivity of collision detection using external sensors will be improved, but its disadvantages are: the collision detection of external sensors will increase the cost of the robot and the complexity of wiring

[0005] The other is not to use external sensors to collect the current and torque changes of each joint of the manipulator, but to convert the read current of the joints of the manipulator into torque, and bring the value of the position encoder into the theoretical dynamic model to obtain the required The driving torque at this moment, the theoretical torque and the actual measured torque are compared to judge the collision situation; this algorithm needs the speed and acceleration of each joint of the manipulator, and the introduction of noise will cause inaccurate detection. Je H et al. The current change difference is compared with the set threshold to detect external force interference; but this method is easy to cause false detection when the manipulator changes direction during the movement process, and also detects collisions by changing the energy of the system. The disadvantages of this method The reason is that it can only detect the external force during the movement process. When the robot arm is stationary, it will affect the accuracy and real-time detection

Some literature (Luca A D, Mattone R.Sensorless Robot Collision Detection and Hybrid Force / MotionControl[C] / / IEEE International Conference on Robotics and Automation.IEEE,2005:999-1004.) adopts a generalized momentum design based on external force observer , this method does not introduce noise interference caused by acceleration, but the gain in the transfer function of the first-order low-pass filter is too small to ensure accuracy and rapidity. In addition, it can only detect continuous and slow external forces, and cannot detect high-speed and sharp external forces.

[0006] Static thresholds can easily lead to false detections. Therefore, a dynamic threshold setting method is proposed to solve the problem of false detections during robot start-stop and operation.

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