scholarly journals Error Analysis by Kinetics for Parallel-Wire Driven System Using Approximated Inverse Kinematics

2018 ◽  
Vol 30 (5) ◽  
pp. 763-771
Author(s):  
Hitoshi Kino ◽  
Takumi Imamura ◽  
Norimitsu Sakagami ◽  
◽  
Keyword(s):  
Inverse Kinematics ◽  
Degrees Of Freedom ◽  
Control Method ◽  
Target Object ◽  
Planar System ◽  
Positioning Control ◽  
Parallel Wire ◽  
Positioning Errors ◽  
Driven System ◽  
The Wire

Parallel-wire driven systems, which use light flexible wires in place of rigid links, control the position of a target object by controlling their wire lengths. In the kinematics for such a parallel-wire driven system, when the relationship between the end-effector position and the wire lengths is investigated, a fixed point for the wire-contacting point on the winding reel in the actuator (or guide pulley) is often approximated to simplify the calculation. The approximated kinematics however could lead to a number of positioning errors in the positioning control. This study proposes a framework for evaluating these positioning control errors by using approximated inverse kinematics. In view of the system dynamics, this study analyzes the positioning control errors for the control method in the wire-length coordinates. We discuss a case study on a two degrees-of-freedom planar system using three wires.

Error Evaluation Method of Approximated Inverse Kinematics for Parallel-Wire Driven System – Basic Study for Three-Wire Planar System –

2016 ◽  
Vol 28 (6) ◽  
pp. 808-818 ◽  
Author(s):  
Hitoshi Kino ◽  
◽  
Nobuhiro Okubo ◽  
Toshihide Ikeda ◽  
Hiroaki Ochi ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Evaluation Method ◽  
Inverse Kinematic ◽  
Basic Study ◽  
Planar System ◽  
End Effector ◽  
Two Degrees Of Freedom ◽  
Parallel Wire ◽  
Positioning Errors ◽  
Driven System

[abstFig src='/00280006/04.jpg' width='300' text='Two-degrees-of-freedom planar system using three wires' ] Parallel-wire driven system, a kind of parallel-link mechanism, employs flexible and light wires in place of rigid links. By applying kinematics to parallel-wire driven systems, we seek to obtain the relationship between the end-effector’s position and wire length. Kinematics usually approximates the wire-contacting point of the winding reel (or guiding pulley) in the actuator unit to be a fixed point. Similar kinematic approximations, however, are likely to cause errors in controlling the end-effector position. In this study, therefore, we attempt to evaluate end-effector positioning errors due to inverse kinematic approximations. As the first step, we analyze end-effector positioning errors in two-degrees-of-freedom planar system and propose two methods to evaluate the positioning errors. Then, we conduct two case studies where we compare the errors due to inverse kinematic approximations and effects of wire’s elastic elements in order to confirm effectiveness of the proposed methods for evaluating end-effector positioning errors.

Study and Implement on Key Technologies of Ship-Welding Mobile Robot

2010 ◽  
Vol 44-47 ◽  
pp. 321-325
Author(s):  
Liang Hua ◽  
Lin Lin Lv ◽  
Ju Ping Gu ◽  
Yu Jian Qiang
Keyword(s):  
Mobile Robot ◽  
Control Method ◽  
Structure Design ◽  
Seam Tracking ◽  
Precision Positioning ◽  
Positioning Control ◽  
Controlling System ◽  
Welding Torch ◽  
Driven System ◽  
And Control

The key technilogies of ship-welding mobile robot applied to ship-building in plane block production line were researched and realized. The mechanical structure design of the robot was completed. The motion-controlling system of of two-wheel differential driving mobile robot was developed. A novel precision positioning control method of welding torch using ultrasonic motors was putforward. The mechanism and control-driven system of precision positioning system for welding torch were completed. The platform of obstacle avoidance navigation system was designed and the strategies of seam tracking, trajectory and posture adjustment were preliminary studied. The methods and results put forward in the paper could act as the base of deep research on the theories and technologies of ship-welding mobile robot.

scholarly journals Design and development of anchoring positioning control system for riprap leveling ship

2021 ◽  
Vol 233 ◽  
pp. 04007
Author(s):  
Xiaotao Hua ◽  
Yan Liu ◽  
Haiyang Sun ◽  
Jianru Chen
Keyword(s):  
Control System ◽  
Equilibrium State ◽  
Degrees Of Freedom ◽  
Wind Wave ◽  
Control Method ◽  
Positioning Control ◽  
Six Degrees Of Freedom ◽  
Hydrodynamic Parameters ◽  
Convergence Control ◽  
Heading Angle

It is very important to level foundation bed by riprap in water and soil engineering. In this paper, a real-time feedback convergence control method is proposed to control the position and heading angle of the riprap leveling ship. The wind, wave, current and hydrodynamic parameters are obtained by empirical formula; the tension of four cables is calculated according to the balance equation of six degrees of freedom, and then the cable deformation is obtained. According to the deformation of the cable, the length of the cable in a certain equilibrium state can be obtained. The length of four cables can be lengthened or shortened by comparing the length of cables at two balanced positions. The length of cables can be controlled by winch to complete the anchoring and positioning control of leveling ship.

An Optimization Method for Solution Selection Based on the Inverse Kinematics Problem of a Mechanical Arm

2015 ◽  
Vol 740 ◽  
pp. 211-217
Author(s):  
Yuan Yuan Luo ◽  
Dong Xu Li ◽  
Cai Zhi Fan
Keyword(s):  
Inverse Kinematics ◽  
Degrees Of Freedom ◽  
Optimal Solution ◽  
Optimization Method ◽  
Target Object ◽  
Operation Process ◽  
Inverse Kinematics Problem ◽  
Simulation And Experiment ◽  
Solution Selection ◽  
Solution Problem

The solution selection problem of inverse kinematics for a mechanical arm is an important factor affecting the robot end effector positioning. This paper takes a real robotic arm of four degrees of freedom grasping the target object as the research background and studies the multi-solution problem of the inverse kinematics. Firstly, the paper establishes the kinematics model of the mechanical arm and solved the inverse kinematics equation by multiplying by the inverse of the coordinate transformation matrix on both sides. Secondly, the paper presents an optimization method based on joint minimization aiming at the multi-solution problem, and deals with the singularity of the mechanical arm by using the method of setting threshold in the process of operation, which can get the optimal solution without suffering singularity problems. Finally, the simulation and experiment results show that the joint angle of the mechanical arm changes smoothly during the operation process and singular points do not occur, verifying the effectiveness of the processing method.

scholarly journals A 4-DOF Upper Limb Exoskeleton for Physical Assistance: Design, Modeling, Control and Performance Evaluation

2021 ◽  
Vol 11 (13) ◽  
pp. 5865
Author(s):  
Muhammad Ahsan Gull ◽  
Mikkel Thoegersen ◽  
Stefan Hein Bengtson ◽  
Mostafa Mohammadi ◽  
Lotte N. S. Andreasen Struijk ◽  
...  
Keyword(s):  
Upper Limb ◽  
Tracking Control ◽  
Degrees Of Freedom ◽  
Control Method ◽  
Mechanical Design ◽  
Trajectory Tracking Control ◽  
Upper Limb Exoskeleton ◽  
And Performance ◽  
Physically Disabled People ◽  
Human Upper Limb

Wheelchair mounted upper limb exoskeletons offer an alternative way to support disabled individuals in their activities of daily living (ADL). Key challenges in exoskeleton technology include innovative mechanical design and implementation of a control method that can assure a safe and comfortable interaction between the human upper limb and exoskeleton. In this article, we present a mechanical design of a four degrees of freedom (DOF) wheelchair mounted upper limb exoskeleton. The design takes advantage of non-backdrivable mechanism that can hold the output position without energy consumption and provide assistance to the completely paralyzed users. Moreover, a PD-based trajectory tracking control is implemented to enhance the performance of human exoskeleton system for two different tasks. Preliminary results are provided to show the effectiveness and reliability of using the proposed design for physically disabled people.

Effects of Dynamic Model Errors in Task-Priority Operational Space Control

Robotica ◽  
2021 ◽  
pp. 1-12
Author(s):  
Paolo Di Lillo ◽  
Gianluca Antonelli ◽  
Ciro Natale
Keyword(s):  
Inverse Kinematics ◽  
Degrees Of Freedom ◽  
Inverse Dynamics ◽  
Null Space ◽  
Control Algorithms ◽  
Model Errors ◽  
Operational Space ◽  
Dynamic Level ◽  
Concurrent Tasks ◽  
Modeling Errors

SUMMARY Control algorithms of many Degrees-of-Freedom (DOFs) systems based on Inverse Kinematics (IK) or Inverse Dynamics (ID) approaches are two well-known topics of research in robotics. The large number of DOFs allows the design of many concurrent tasks arranged in priorities, that can be solved either at kinematic or dynamic level. This paper investigates the effects of modeling errors in operational space control algorithms with respect to uncertainties affecting knowledge of the dynamic parameters. The effects on the null-space projections and the sources of steady-state errors are investigated. Numerical simulations with on-purpose injected errors are used to validate the thoughts.

scholarly journals Torque Ripple Suppression of PMSM Based on Robust Two Degrees-of-Freedom Resonant Controller

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1015
Author(s):  
Mingfei Huang ◽  
Yongting Deng ◽  
Hongwen Li ◽  
Jing Liu ◽  
Meng Shao ◽  
...  
Keyword(s):  
Control Strategy ◽  
Measurement Errors ◽  
Degrees Of Freedom ◽  
Control Method ◽  
Torque Ripple ◽  
Current Loop ◽  
Two Degrees Of Freedom ◽  
Robust Stability Analysis ◽  
Resonant Controller ◽  
Testing Environments

This paper concentrates on a robust resonant control strategy of a permanent magnet synchronous motor (PMSM) for electric drivers with model uncertainties and external disturbances to improve the control performance of the current loop. Firstly, to reduce the torque ripple of PMSM, the resonant controller with fractional order (FO) calculus is introduced. Then, a robust two degrees-of-freedom (Robust-TDOF) control strategy was designed based on the modified resonant controller. Finally, by combining the two control methods, this study proposes an enhanced Robust-TDOF regulation method, named as the robust two degrees-of-freedom resonant controller (Robust-TDOFR), to guarantee the robustness of model uncertainty and to further improve the performance with minimized periodic torque ripples. Meanwhile, a tuning method was constructed followed by stability and robust stability analysis. Furthermore, the proposed Robust-TDOFR control method was applied in the current loop of a PMSM to suppress the periodic current harmonics caused by non-ideal factors of inverter and current measurement errors. Finally, simulations and experiments were performed to validate our control strategy. The simulation and experimental results showed that the THDs (total harmonic distortion) of phase current decreased to a level of 0.69% and 5.79% in the two testing environments.

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