Feel lonely? What about reading books? Book is one of the greatest friends to accompany while in your lonely time. When you have no friends and activities somewhere and sometimes, reading book can be a great choice. This is not only for spending the time, it will increase the knowledge. Of course the b=benefits to take will relate to what kind of book that you are reading. And now, we will concern you to try reading modelling and control of robot manipulators as one of the reading material to finish quickly.

Modelling and Control of Robot Manipulators

Use of sensors in robotic welding for controlling the weld quality leads to replacement of manual welding operation in dangerous work environment in presence of high temperature and fumes even in small or medium scale enterprises. The seam tracking operation is very essential for extracting weld seam position which can be fed to robot controller for instructing robot along the weld seam path. The seam tracking operation can be executed by different types of sensors having their own merits and demerits. In this paper, different sensors and techniques used for seam tracking task in robotic welding have been discussed in detail. Each sensor has different method or technology of weld seam feature extraction which have been described by different authors in different ways. The chief tasks for seam tracking have been found to be weld starting and end point detection, weld edge detection, joint width measurement and weld path position determination with respect to robot co-ordinate frame. Thus sensors have a very important role in robotic welding for fully automating the system with in process real time monitoring of weld process parameters with the sensor feedback. In further discussion the practical use of different sensors in industries with a comparison of their advantages and disadvantages have been discussed. This Paper presents the role of sensors in robotic welding and a detail study of methodologies of weld seam position and geometry feature extraction by different sensors typically used for weld seam tracking.

Advances in weld seam tracking techniques for robotic welding: A review

Application of novel force control strategies to enhance robotic abrasive belt grinding quality of aero-engine blades

A new strategy for ensuring human safety during various levels of interaction with industrial robots

The estimation of the ten inertial parameters of rigid loads, which are attached to manipulators, may benefit several robotics applications, e.g.: force control, object recognition, and pose estimation. These applications require sufficiently accurate, robust, and fast estimation of the inertial parameters. Existing approaches, however, do not allow for robust on-line estimation, since they use standard batch least-squares techniques, which ignore noise in the data matrix. The proposed approach, however, estimates the inertial parameters on-line and very fast (approx. 1.5s), while explicitly considering noise in the data matrix by a total least-squares approach. Apart from estimation equations and estimation approaches, the design of estimation trajectories is addressed in this paper. The performance of the proposed estimation approach is compared with the recursive ordinary least-squares (RLS) and the recursive instrumental variables (RIV) method. Experimental results clearly recommend the proposed recursive total least-squares approach (RTLS).

On-line estimation of inertial parameters using a recursive total least-squares approach

This article presents an algorithm for dynamic force/torque measurement and robot load identification using the so called 12DOF sensor to measure forces/torques and linear/angular accelerations. The basic equations of dynamic forces and torques arising during robot motion and acting on the end-effector were worked out. To be able to perform the experiments suitable robot system based on a six axes articulated manipulator was constituted. For this system also the appropriate software was developed. The load parameters of the tool were determined during particular motion sequence of the robot and the values were compared with values from CAD software. The compensation of dynamic forces and torques is verified using the experimental robot system and the results are presented.

Dynamic force/torque measurement using a 12DOF sensor

This paper deals with controller features which improve force controlled contour following. This kind of robot force control may by used in surface finishing tasks like polishing, deburring or grinding. The already introduced proportional controller with positive position feedback brought very good results in force control of a position controlled robot in both impact and contact phase. If the characteristics of the environment which should be finished with the robot tool are not constant, unfavorable contact forces may occur which can damage the tool or the workpiece. For the purpose of adapting the current inclination angle between robot end-effector and environment we investigate the insertion of an additional integrator into the force controller. Thereby, it will be possible to reduce static control errors. However, more attention should be paid during its parameterization with respect to the stability boundary of the closed loop control. Another novel feature in this paper is the variation of the end-effector velocity as a function of the force control error. With this idea force peaks can be decreased or the loss of contact between robot end-effector and environment can be avoided, e.g. when the inclination angle of the environment changes. All algorithms proposed in this paper are successfully verified by practical experiments.

Force controlled contour following on unknown objects with an industrial robot

This article deals with the interaction between humans and industrial robots, more specifically with the new design and implementation of an algorithm for force-guided motions of a 6-d.o.f. robot. It may be used to comfortably teach positions without using any teaching pendant or for some assistance tasks. For this purpose, from readings of the force/torque sensor mounted in the robot wrist, the gravity forces and torques first have to be eliminated. To control the robot in joint space, it is then convenient to transform the external force and torque values from Cartesian space into joint space using the manipulator transposed Jacobian. This is why with the present approach the Jacobian matrix of the robot used was calculated. Now, from the computed joint torques, suitable position commands of the robot arm can be generated to obtain the desired behavior. A suggestion for this desired behavior is also included in this article. It is based on the impedance control approach in joint space. The proposed algo...

Force-guided motions of a 6-d.o.f. industrial robot with a joint space approach

This paper investigates simple position based force control algorithms for an industrial robot. A lot of approaches to robot force control published in the previous three decades are difficult to implement in commercial robot controllers. This fact is one reason why force controlled robots rarely appear in industrial applications. On the other side force control may improve some robot tasks like automated assembling or material processing. Therefore, is seems to be necessary to concentrate on simple controller structures on the field of robot force control which are easily realizable and adjustable. For this purpose in this paper linear standard control algorithms have been selected and implemented with a real robot. One proposed structure is the proportional controller with positive position feedback which dealt probably here for the first time and shows very good control behavior. Some proposals to parameterization of different controllers are given and their performance with respect to contact detection, impact and response to setpoint changes is shown and compared by practical experiments.

Position feedback in force control of industrial manipulators - An experimental comparison with basic algorithms

In robotic contour following tasks such as sewing, grinding or applying adhesives, the robot moves a tool along a desired path on a workpiece. In order to compensate inaccuracies of the path definition a vision system can be used to guide the robot during task execution. This paper presents an algorithm to adjust the position and orientation of the tool by predictive vision-based control that compensates system delays caused by the robot dynamics and the vision sensor. Our system includes feature validation for suppressing optical disturbances; tool alignment with minimum angular tracking error along unknown contours; and restricting the tool velocity online depending on the applicable angular velocities. Our experimental setup uses an industrial laser-camera-triangulation sensor providing taught features in 3D such as a visible edge along the surface of the workpiece. The paper includes experimental results of robotic contour following using a wavy compliant surface to validate the approach.

Jozef Suchy

Papers

Dynamic force/torque measurement using a 12DOF sensor

Force controlled contour following on unknown objects with an industrial robot

Force-guided motions of a 6-d.o.f. industrial robot with a joint space approach

Position feedback in force control of industrial manipulators - An experimental comparison with basic algorithms

Predictive robotic contour following using laser-camera-triangulation