Load dynamics identification

Abstract

In this chapter we present experimental results concerning identification of dynamic parameters of a load hold by a robot. There are ten dynamic parameters of the load namely mass, three parameters of the centre of mass multiplied by its mass, and six parameters of the inertia tensor, all together, ten parameters. These parameters are expressed in local coordinate frame which is associated with the load and therefore they are constant. Experimental identification of this set of parameters is quite difficult because we need very specialised equipment in order to carry out the experiments. Of course we can measure and weigh the load and then calculate all the parameters, but we want to do it experimentally, during the movement of the robot, assuming that the robot grasps the load which is a completely unknown object. The most expensive part is the force/torque sensor which has to be mounted between the wrist and the gripper. As mentioned in Chapter 2 Chair of Control, Robotics, and Computer Science has two force/torque sensors. The sensor allows us to measure forces and torques in the local coordinate frame associated with it. Three components of the forces and torques are measured in three dimensional space. Note, that in case considered here we need measurements of the forces and torques in three dimensions because these forces and torques are not compensated for by the structure of the gripper. In the case of joint generalised forces measurements, we can assume that the sensor measures only the forces and torques along the axis of translation and rotation, respectively.