Tracking Control of Redundant Manipulators with Singularity-Free Orientation Representation and Null-Space Compliant Behaviour

This paper presents a suitable solution to control the pose of the end-effector of a redundant robot along a pre-planned trajectory, while addressing an active compliant behaviour in the null-space. The orientation of the robot is expressed through a singularity-free representation form. To accomplish the task, no exteroceptive sensor is needed. While a rigorous stability proof confirms the developed theory, experimental results bolster the performance of the proposed approach

Kinematic synthesis of over-constrained double-spherical six-bar mechanism

The main problem in the synthesis of any mechanism is the fact that the objective function of the mechanism, which will be synthesized, should be found and simplified by using appropriate algebraic method. Finding objective function and calculation process can become complicated especially when the number of design parameters is increased for the over-constrained mechanisms. A new technique for solving the kinematic synthesis of over-constrained double-spherical six-bar mechanism is developed and applied in this work. Interpolation approximation is used during synthesis procedure. A numerical example for the kinematic synthesis procedure is given to validate the theory in application

A Robot Arm Design Optimization Method by Using a Kinematic Redundancy Resolution Technique

Redundancy resolution techniques have been widely used for the control of kinematically redundant robots. In this work, one of the redundancy resolution techniques is employed in the mechanical design optimization of a robot arm. Although the robot arm is non-redundant, the proposed method modifies robot arm kinematics by adding virtual joints to make the robot arm kinematically redundant. In the proposed method, a suitable objective function is selected to optimize the robot arm’s kinematic parameters by enhancing one or more performance indices. Then the robot arm’s end-effector is fixed at critical positions while the redundancy resolution algorithm moves its joints including the virtual joints because of the self-motion of a redundant robot. Hence, the optimum values of the virtual joints are determined, and the design of the robot arm is modified accordingly. An advantage of this method is the visualization of the changes in the manipulator’s structure during the optimization process. In this work, as a case study, a passive robotic arm that is used in a surgical robot system is considered and the task is defined as the determination of the optimum base location and the first link’s length. The results indicate the effectiveness of the proposed method

A new objective function for obstacle avoidance by redundant service robot arms

The performance of task-space tracking control of kinematically redundant robots regulating self-motion to ensure obstacle avoidance is studied and discussed. As the subtask objective, the links of the kinematically redundant assistive robot should avoid any collisions with the patient that is being assisted. The shortcomings of the obstacle avoidance algorithms are discussed and a new obstacle avoidance algorithm is proposed. The performance of the proposed algorithm is validated with tests that were carried out using the virtual model of a seven degrees-offreedom robot arm. The test results indicate that the developed controller for the robot manipulator is successful in both accomplishing the main-task and the sub-task objectives.Scientific and Technological Research Council of Turkey (113E147

General subtask controller for redundant robot manipulators

12th International Conference on Control, Automation and Systems, ICCAS 2012; Jeju; South Korea; 17 October 2012 through 21 October 2012This paper will utilize the property of self-motion for redundant robot manipulators by designing the general subtask controller that control the joint motion in the null-space of the Jacobian matrix. The general subtask controller is used for minimizing the total joint motion and for singularity avoidance in this study. Specifically, objective function for each subtask is formed and then the gradient of the objective function is used in the subtask controller to either minimize the joint motion or avoid singularities while tracking a given end-effector trajectory. A 7-DOF LWA4-Arm (SCHUNK) is modeled first in SolidWorks® and then converted to MATLAB® Simulink using SimMechanics CAD translator for the simulation tests of the controller. The kinematics and dynamics equations are derived to be used in the controllers and the simulation results are presented for the 7-DOF redundant robot manipulator operating in 3D space. © 2012 ICROS.Marie Curie International Reintegration Grant within the 7th European Community Framework Programm

Function generation with two loop mechanisms using decomposition and correction method

Method of decomposition has been successfully applied to function generation with multi-loop mechanisms. For a two-loop mechanism, a function y = f(x) can be decomposed into two as w = g(x) and y = h(w) = h(g(x)) = f(x). This study makes use of the method of decomposition for two-loop mechanisms, where the errors from each loop are forced to match each other. In the first loop, which includes the input of the mechanism, the decomposed function (g) is generated and the resulting structural error is determined. Then, for the second loop, the desired output of the function (f) is considered as an input and the structural error of the decomposed function (g) is determined. By matching the obtained structural errors, the final error in the output of the mechanism is reduced. Three different correction methods are proposed. The first method has three precision points per loop, while the second method has four. In the third method, the extrema of the errors from both loops are matched. The methods are applied to a Watt II type planar six-bar linkage for demonstration. Several numerical examples are worked out and the results are compared with the results in the literature

Model based verification of neuroboscope system

NeuRoboScope projesinde, endoskopik hipofiz cerrahisinde kullanılan optik-kamera sisteminin, cerrahın kullandığı cerrahi aletleri takip ederek yönlendirilmesini amaçlayan emniyet kritik bir sistemin tasarlanması amaçlanmıştır. Bu bildiri, sistem gereksinimleri üzerinden tüm sistemin modellenmesini ve oluşturulan bu modelin sınanmasını ele almaktadır. Böylece, tasarım evresinden önce tasarımın dayanağı olan sistem gereksinimlerinin doğrulanması hedeflenmiştir. Sistem bir zamanlı otomat ağı olarak modellenmiş ve UPPAAL model sınama aracı kullanılarak, sistemin başta emniyet kritik olmak üzere diğer önemli özellikleri sınanmıştır.In the NeuRoboScope project, it is aimed to design a safetycritical system that navigates the optical-camera system used in the endoscopic pituitary surgery by tracking the surgery tool that the surgeon uses. This study presents modeling the system upon the requirements and verification of this model, which allows to validate the system requirements before the design phase. Using UPPAAL model checking tool, the entire system is modeled as a network of timed automata and verified against the vital system properties, including particularly the safety critical ones.TÜBİTAK Proje Numaraları: 115E725 ve 115E72