A continuous task transition algorithm for operational space control framework (original) (raw)
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Robot Control near Singularity and Joint Limit Using a Continuous Task Transition Algorithm
International Journal of Advanced Robotic Systems, 2013
When robots are controlled in the task space, singularities and joint limits are among the most critical and difficult issues that can arise. In this paper, we propose a new approach for the robots to operate in the regions near singularities and joint limits using the operational space control framework. Specifically, a continuous task transition algorithm called the intermediate desired value approach is applied to the hierarchically structured controller in the operational space control framework. In this approach, new tasks are defined for dealing with singularities and joint limits, and the tasks are activated or deactivated using the continuous task transition algorithm to guarantee the continuous execution of the tasks during the execution of the main task. The proposed approach is implemented on a 6-DOF manipulator called Roman-MD. The experimental results demonstrate its performance near the singular regions and joint limits.
An analysis of the operational space control of robots
2010 IEEE International Conference on Robotics and Automation, 2010
Theoretically, the operational space control framework [1] can be regarded to be the most advanced control framework for redundant robots. However, in practice, the control performance of this framework is significantly degraded in the presence of model uncertainties and discretizing effects. Using the singular perturbation theory, this paper shows that the same model uncertainties can create different effects on the task space and joint space control performance. From the analysis, a multi-rate operational space control was proposed to minimize the effects of model uncertainties on the control performance and while maintaining the advantages of the original operational space framework [2]. In this paper, we present a stability analysis of the multi-rate operational space control framework using the Lyapunov's direct method.
A general singularity avoidance framework for robot manipulators: task reconstruction method
IEEE International Conference on Robotics and Automation, 2004. Proceedings. ICRA '04. 2004, 2004
There are several kinds of singularity in controlling robotic manipulator. Among those, the kinematic and algorithmic singularity avoidance have been investigated intensively. What seems to be lacking, however, is excessive performance reduction in non-singular region and difficulty in performance tuning. In this paper, we develop a new method to solve kinematic and algorithmic singularities using task reconstruction approach. This new method drives the manipulator singularity-free path, and simultaneously guarantees task performance. And it can be easily extended singularity avoidance of multiple tasks case in task priority based method of redundant manipulators. The advantage and performance of the proposed method is validated by simulation works.
Automatic singularity avoidance using joint variations in robot task modification
IEEE Robotics & Automation Magazine, 1994
In recent years the research community has addressed the need to improve the flexibility of robot systems. Tlvo particular concepts that have resulted from this research are off-line programming and modular tooling. These concepts are directed at allowing the robot system to be used to perform a variety of tasks with minimal setup time and to allow easy replication of an application. Both of these concepts require that the robot system have the ability to measure the position and orientation of features in the workspace. These measurements can then be used to perform coordinate transformations on each of the task data points. These modified task data points then, theoretically, facilitate the performance of the task by the robot system without human intervention. This luas supported in pmt by frorn IBM Comafim, &tin, designed for specific tasks. turing applications took a T~~.
IFAC Proceedings Volumes, 2014
This paper presents a novel control architecture for operational space control when the end effector or the robotic chain is kinematically constrained. Particularly, we address kinematic control of robots operating in the presence of obstacles such as point, plane, or barrier constraints imposed on a point on the manipulator. The main advantage of the proposed approach is that we are able to control the end-effector motion in the normal way using conventional operational space control schemes, and by rewriting the Jacobian matrix we also guarantee that the constraints are satisfied. The most challenging problem of obstacle avoidance of robotic manipulators is the extremely complex structure that arises when the obstacles are mapped from the operational space to joint space. We solve this by first finding a new set of velocity variables for a point on the robot in the vicinity of the obstacle, and on these new variables we impose a structure which guarantees that the robot does not hit the obstacle. We then find a mapping denoted the Constrained Jacobian Matrix from the joint variables to these new velocity variables and use this mapping to find a trajectory in joint space for which the constraints are not violated. We present for the first time the Constrained Jacobian Matrix which imposes a kinematic constraint on the manipulator chain and show the efficiency of the approach through experiments on a real robot.
A framework for the analysis and control of manipulator systems with respect to the dynamic behavior of their end-effectors is developed. First, issues related to the description of end-effector tasks that involve constrained motion and active force control are discussed. The fundamentals of the operational space formulation are then presented, and the unified approach for motion and force control is developed. The extension of this formulation to redundant manipulator systems is also presented, constructing the end-effector equations of motion and describing their behavior with respect to joint forces. These results are used in the development of a new and systematic approach for dealing with the problems arising at kinematic singularities. At a singular configuration, the manipulator is treated as a mechanism that is redundant with respect to the motion of the end-effector in the subspace of operational space orthogonal to the singular direction.
A singularity-free motion control algorithm for robot manipulators—a hybrid system approach
Automatica, 2004
This paper presents the design and implementation of a singularity-free tracking algorithm for robot manipulators using a hybrid system approach. A hybrid robot motion controller is designed to ensure feasible robot motion in the neighborhood of kinematic singularities. The hybrid control system has a two-layered hierarchical structure, a discrete layer and a continuous layer. The robot workspace is partitioned into subspaces based on the singular conÿgurations of the robot. Switching between continuous controllers is involved when the robot travels across the subspaces. With the hybrid controller, the robot can work at the vicinity of singular conÿgurations, but also can go through and stay at the singular conÿgurations. The stability of the hybrid system is investigated using multiple Lyapunov function theory. Experimental results have demonstrated the advantages of the hybrid robot motion control method. ?
Real-time dynamic singularity avoidance while visual servoing of a dual-arm space robot
Proceedings of the 2015 Conference on Advances In Robotics, 2015
Singularity of robotic manipulators is an important issue in the stability and control of autonomous robotic systems. This paper presents a real-time dynamic singularity avoidance approach for such autonomous free-floating space robots where visual servoing is used as feedback in the control loop. The proposed method uses manipulability measure as distance criteria and does not require any prior knowledge of singular configurations. Velocities in task space are projected on a surface of constant manipulability measure to avoid singular configurations. Numerical experiments are carried out, to validate the proposed method, on a 6-Degrees-of-Freedom dual-arm space robot mounted on a service satellite.
Kinematic control of redundant robots with guaranteed joint limit avoidance
Robotics and Autonomous Systems, 2016
h i g h l i g h t s • A novel kinematic control signal guaranteeing joint limit avoidance is proposed. • In sensor driven tasks it generates feasible paths to the target. • With planned task trajectories it can act as a null-space velocity. • Smooth joint trajectories and accurate target reaching are achieved. • Experimental results with a KUKA LWR4+ manipulator demonstrate its performance.