This paper presents the motion control of a six degree-of-freedom tendon-based parallel manipulator, which moves a platform with high speed using seven cables. To control the motion of the platform along desired trajectories in space, nonlinear feedforward control laws in the cable length coordinates are used. Taking account of the effect of redundancy on actuation, the optimal tension distribution should be considered to the advantage of the control laws. Using a method based on the analysis of the workspace condition, tension constraints and limiting torque constraints of actuators, an analytical solution for optimum tension distribution was found and used to compute the force in each cable for compensation of dynamic errors. It is experimentally demonstrated that the proposed control laws reduce the energy consumption of the actuators and satisfy the path tracking accuracy.

Motion control of a tendon-based parallel manipulator using optimal tension distribution

In this paper, methods based on various spline techniques for planning and fast modifications of a trajectory for robot manipulators are investigated. Algebraic and trigonometric splines, their combined use, and the use of the B-spline technique are analyzed and compared in detail. In so doing, we focus on the performance of sudden changes in a predefined trajectory, e.g. obstacle avoidance in real-time applications. Some comparative examples illustrate our results.

Planning and real-time modifications of a trajectory using spline techniques

An increasing need for automated or partly automated sequences of operation in building industry, agriculture, forestry, mining, scrap yards or other working fields with rough and unstructured environment requires machines, cranes, excavators or manipulators which are able to operate autonomously or operator-assisted under rapidly changing working conditions. In this paper, the modelling, simulation and control design of newly projected large, and mobile heavy manipulators which are typical examples of mechatronic systems will be presented. The various techniques are demonstrated by three different examples related to industrial projects.

Modelling simulation and control design for large and heavy manipulators

The system under investigation is the hydraulically driven autonomous large scale-combined legged and wheeled vehicle, the anthropomorphically legged and wheeled Duisburg robot (ALDURO). In this paper, a complete mechatronic simulation model, realized in the object-oriented programming language C++, is presented. It contains the mechanical system including an explicit solution of the kinematic loops, a model of the ground contact, and the dynamics of the complete hydraulic system, as well as a force-based motion control concept based on an exact input-output linearization using decentralized force controllers. Some simulation results are shown to demonstrate the function of the simulation model and the control concept presented.

Modeling, simulation, and model-based control of the walking machine ALDURO

Modelling, simulation and control design for large and heavy manipulators

Modelling, Simulation and Control of Flexible Manipulators

A detailed dynamic model of hydraulically driven mobile large-scale manipulators is presented. The model can be used as simulation model, for the calculation of the forces in the design process and for the development of the controllers, which are required for tracking given trajectories, but also to avoid vibrations. It takes into account all relevant coupling effects between hydraulic drives and arm elements as well as between flexible deformations and large nonlinear rigid body motion. The control concept makes use of the redundancy of the system in order to avoid collisions.

Dynamic Simulation, Nonlinear Control and Collision Avoidance of Hydraulically Driven Large Redundant Manipulators

The control tasks for the investigated manipulators are tracking prescribed trajectories and avoiding collisions with obstacles in the three dimensional workspace. The most important problems one has to deal with are the complexity of the system with a highly nonlinear kinematic and dynamic behavior, the nonlinear friction and elasticity of the hydraulic drives and the redundant structure of the arm package. In this paper two different concepts for controlling the hydraulic actuators are presented, both using the method of exact input output linearization.

Nonlinear Motion Control of Hydraulically Driven Large Redundant Manipulators

The application of large manipulators in servicing and building environments is a field of growing research interest. Typical tasks performed by the manipulators are pumping of wet concrete, handling of loads under difficult conditions and cleaning of aircraft. One of the main problems is the occurence of vibrations induced by hydraulic pressure oscillation and elasticity effects. In order to suppress these vibrations and to coordinate the motion for tracking given trajectories, a nonlinear position control concept is required. In this paper, a particular method is developed for this purpose, taking into account effects of mechanical transmission elements, hydraulic actuators and boom flexibility. As an application, the control of a large-scale manipulator carrying out wet concrete pumping tasks is presented.

Vibration Suppressing for Hydraulically Driven Large Redundant Manipulators

Hydraulically driven large-scale manipulators are complex mechatronic systems with highly nonlinear dynamic behaviour. For an easier understanding of this behaviour a nonlinear dynamic simulation model is required, taking into account all relevant coupling effects between hydraulic drives and arm elements as well as between flexible deformations and overall nonlinear rigid body motion. The model also serves as the basis of a nonlinear position control concept for tracking prescribed trajectories and for avoiding vibrations arising due to the elasticities in the system. The redundancy of the arm assembly can be used to avoid collisions with obstacles in the three dimensional workspace. Regarding numerical aspects, it is shown that the applied kinetostatic method has great advantages.

Modelling, simulation and control of a large hydraulically driven redundant manipulator with flexible links. Modell, Simulation und Regelung eines großen redundanten Manipulators mit flexiblen Gelenken und Hydrauliksteuerung

Martin Schneider

Papers

Modelling, Simulation and Control of Flexible Manipulators

Dynamic Simulation, Nonlinear Control and Collision Avoidance of Hydraulically Driven Large Redundant Manipulators

Nonlinear Motion Control of Hydraulically Driven Large Redundant Manipulators

Vibration Suppressing for Hydraulically Driven Large Redundant Manipulators

Modelling, simulation and control of a large hydraulically driven redundant manipulator with flexible links. Modell, Simulation und Regelung eines großen redundanten Manipulators mit flexiblen Gelenken und Hydrauliksteuerung