Force/ Position Control Based on PSO and Approximately Jacobian for 3-DOF Parallel Robot for Bone Drilling

A new six degree-of-freedom parallel robot with three limbs for high-speed operations

In this paper a novel orthogonal 6-DOF (Degree Of Freedom) parallel robot with redundant actuation is studied as an earthquake motion simulator. Taking the practical simulation of earthquake waves into consideration, we firstly analyze the general characteristics of natural earthquakes. Complexity and variety of seismic waves, 3-dimension and multi-DOF movement and strong devastating force are regarded as their three obvious features in this article. Based on the characteristics of this novel orthogonal 6-DOF parallel mechanism with redundant actuation and the features of earthquakes, the feasibility of using this parallel robot as an earthquake motion simulator is analyzed. In order to simulate earthquake motion by using the parallel robot, its unambiguous kinematics and dynamics models are derived in details. The control system of the proposed earthquake simulator is developed based on the PXIbus development platform. A typical three-direction earthquake motion, the El Centro earthquake, is simulated on the end-effector of the parallel robot using its mathematical models and control system. Three main motion parameters of simulated seismic waves, displacements, velocities and accelerations are measured respectively. The experimental results show that this equipment is appropriate for using as an earthquake simulator.

Screw theory was introduced and inducted to the statics analysis and calculation of 6-DOF (Degree of Freedom) parallel robot. Based on the scheme, a 6-DOF parallel robot--hydraulic Stewart test platform was checked specially. The results reveal that, the platform design is appropriate, the analysis procedure is concise and the calculation operation is simple and convenient.

A novel 6-degree-of-freedom (6-DOF) parallel robot driven by six novel linear motors is designed and controlled in this paper. Detailed structures of linear motors are illustrated. A control strategy based on kinematics of the 6-DOF parallel robot is used, and six linear motors are controlled to track their own desired trajectories under a designed fractional-order active disturbance rejection controller (FOADRC). Compared with the normal ADRC, two desired trajectories and three different working situations of a linear motor are simulated to show good performances of the FOADRC. Experimental results show that six linear motors can track their own desired trajectories accurately under payloads and disturbances, and the novel 6-DOF parallel robot can be controlled well.

The aim of this study is to optimize a 2-dof micro parallel robot. Parallel robots potential is only then efficient exploited when their structure is optimal dimensioned from geometric point of view. So, their performances depend very strong on their geometry. Thus, optimization of the geometric parameters or optimal dimensioning has become an important issue for improving the parallel robots performances. Here, intended to show the advantages of using the GA, we applied it to an optimization problem of 2 DOF parallel robot. The obtained results have shown that the use of GA in such kind of optimization problem enhances the quality of the optimization outcome, providing a better and more realistic support for the decision maker.

A new structure of an 8-input 6-DOF (degree-of-freedom) parallel robot is introduced, and its inverse kinematics is built up. Based on the hormone modulation of neuroendocrine system, we present an intelligent controller to be suitable for the characteristics of the 8-input 6-DOF parallel robot with redundant drivers. We choose intelligent PID controller as the basic controller, the parameter of PID is adjusted real-time by the principle of regulating cortin and the characteristic of parallel manipulator. Since it is difficult to build the exactly dynamics model of the parallel robot, we make use of the SimMechanics in MATLAB to build the machine system model and then control it with the proposed intelligent controller. The simulation result shows that the controller can control the movement of the robot effectively. They can restrain the bad influence of the parameter and load change of parallel manipulator.

Development of invers kinematic method for 6-dof parallel robot using analytical approach

Although a parallel robot is operated at high speed, its work space is relatively narrow, compared to that of a SCARA (Selective Compliance Assembly Robot Arm) robot or an articulated robot. It is anticipated that if a 3-DOF (Degrees Of Freedom) wrist mechanism is added to a pick-and-place 3-DOF parallel robot with the increased workspace by using an additional straight axis at its top, then the overall 6-DOF parallel robot has an increased degrees of freedom as well as a high velocity within wider workspace. Thus this kind of parallel robot has a wider workspace so that the application of the robot to the assembly of small-sized mechanical components and electronic components or the processing process will increase. This paper aims to offer a way of testing stability when selecting gears, in order to reduce the weight of a 3-DOF wrist mechanism for a pick-and-place 3-DOF parallel robot with the increased workspace by using an additional straight axis at its top. We will perform SolidWorks <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> modeling- and ANSYS <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">®</sup> -based structural analysis of a pinion gear, which is most vulnerable to the force from a 3-DOF wrist mechanism, in order to lighten the robot weight for various tasks to perform. Although there is no need to get equal theoretical values and analysis results, because individual gears have different forms of teeth, somewhat approximate values should be obtained when there is no mistake in analysis conditions. If initial analysis results considerably differ from theoretical values that are calculated in advance, we will check if there is something wrong with contact conditions or input values. Ultimately, it is anticipated that this methodology presented in this paper will help in mitigating mistakes during analysis and looking for accurate values for a lightweight 3-DOF wrist mechanism for a parallel robot with expanded workspace.

In this paper, the trajectory tracking control problem is addressed for a pneumatically actuated 6- DoF Gough-Stewart parallel robot. At first, dynamic model of the pneumatic system of each link of the robot which comprises a pneumatic actuator and a proportional electrical control valve is extracted. Unknown parameters of the obtained dynamic model consisting friction force, viscous coefficient and the parameters of the valve are identified by employing an evolutionary algorithm. Then, position control of the robot's pneumatic actuator is investigated based on designing Backstepping-Sliding Mode controller according to the nonlinear dynamic model of the pneumatic system. Moreover, kinematic equations of the 6- DoF parallel robot are achieved and a novel method is proposed, the so-called Geometry-based Quasi-Forward Kinematic, which calculates position of the end-effector of the robot without using expensive position sensors. Accordingly, kinematically closed-loop control of the parallel robot, which is based on simultaneous joint space and task space control, is investigated for trajectory tracking using potentiometers, a rotation sensor and based on the computed position of the end-effector by the proposed method. Desired sinusoidal pure rotations and translations are tracked in which root mean square error of the pure translations and rotations are lower than 1.3 (cm) and 2.6 (deg), respectively. The experimental results reveal that trajectory tracking control of the pneumatic 6-DoF Gough-Stewart parallel robot performs properly based on the proposed control strategies and the novel method for calculating position of the end-effector.

The design complexity of parallel robots is due to the number of strictly interrelated functional and structural problems. Lower DOF parallel robot rely on strictly geometrical constraints of axis of pairs in and between limbs to obtain the reduced number of DOF. In practice, these constraints will never been perfectly fulfilled due to the inevitability of errors, and hence produce series bad effects and problems. Using screw theory and set theory as mathematical tools, the DOF and constraint system of 4-DOF parallel robot, were systematically summarized and in-depth studied. Kinematic design of a limited DOF parallel robot, is presented that takes into account the error. The errors presented in the paper consist of two kinds. The errors is defined as the position error of rotation center DOF the platform caused by errors in the kinematics constants, such as axis error The above research results provided an insight into the error of 4-dof parallel robot

Parallel robots have been used in a large number of applications ranging from astronomy to flight simulators and are becoming increasingly popular in the field of construction industry. This paper is aimed at presenting a study on the optimization of the BIGLIDE and BIPOD parallel robots, which comprises two-degree-of-freedom (DOF) parallel robots with constant and variable struts. The robot workspace is characterized and the inverse kinematics equation is obtained. In the paper, design optimization is implemented with Genetic Algorithms (GA) for optimization considering transmission quality index, design space and workspace. Here, intended to show the advantages of using the GA, we applied it to a multicriteria optimization problem of 2 DOF parallel robots. Genetic algorithms (GA) are so far generally the best and most robust kind of evolutionary algorithms. A GA has a number of advantages. It can quickly scan a vast solution set. Bad proposals do not affect the end solution negatively as they are simply discarded. The obtained results have shown that the use of GA in such kind of optimization problem enhances the quality of the optimization outcome, providing a better and more realistic support for the decision maker. Considering its high load capacity and geometrical dexterity, the system is appropriate for maintenance, building construction, and cleaning of large and dangerous structures.

A sliding mode controller with an integral-operation switching surface for 2- DOF parallel robot, which is derived by AC servo motors, is designed in this paper. Firstly, the variable structure controller with an integral operation switching surface is proposed to make the system of the parallel robot possess the properties of the insensitivity to the uncertainties and external disturbance. Next, the adaptive law is designed to achieve the online identify estimation of the system uncertainties of the parallel robot. Simulation results show that, by adopting the proposed control method in the parallel robot control system, the chattering of the conventional sliding mode control is alleviated, the practicability of the control system is improved through adjusting the controller's parameters timely in terms of the identified results and the control system has a perfect robust performance.

The Stewart-Gough Platform (SGP) is defined as a 6-DOF parallel robot. It consists of two rigid plates; moving platform (MP) in top and base platform (BP) in bottom and also six actuating links that connect them to each other and provide up to six DOF for the MP with respect to the BP. SGP's impressive features are high load carrying capacity, low inertia, high stiffness, better repetition and precise positioning. This paper focuses on the accuracy enhancement of a six DOF SGP robot through kinematic calibration. In this method minimum number of sensors have been used for SGP kinematic calibration. This method is presented with details and is implemented on an experimental robot. The assumption of the methodology is that the orientation of MP can be measured by two inclinometers. Calibration involves of a nonlinear function optimization with 36 unknown parameters. Nonlinear least square scheme is used for the optimization. Experimental studies reveal that the proposed method is effective in enhancing the SGP accuracy. The main contribution of this work is implementation of the proposed method on an experimental robot and achievement acceptable results by position control of SGP in joint space. The robot position is controlled in the joint space; results show that calibrated robot follows command signal more accurate than before the calibration.

This paper proposes a new configuration of a 3 DOF parallel robot which uses revolute and spherical joints. It also presents the inverse kinematic model and proposes a PID-type controller with tracking to asymptotically track a desired reference trajectory. This 3 DOF parallel robot can be utilized as a motion simulator or ankle rehabilitator robot. Some simulations were performed with the virtual prototype in MD ADAMS software to verify the performance of the PID-type controller. Finally, preliminary experimental tests using a physical prototype are presented as well.

The paper presents design and control simulations of ISOGLIDE3 parallel robot. An innovative user interface for high-level control of a 3 DOF parallel robot is also pre-sented. The robot interface using virtual reality was veri-fied and tested, and results in MATLAB, Simulink, and SimMechanics were presented. The ISOGLIDE3 robot offers the superior characteristics with regards to the other parallel manipulators, such as the light weight construc-tion. The presented 3 DOF parallel robot can be used for surgery due to its overall precision, good dynamic behav-ior.