Serial-robot Wrist-singularity Mitigation Along Alternative Optimally Adjusted Paths

2021 ◽  
Author(s):  
Paul H. Milenkovic
Keyword(s):  
Kinematic Model ◽  
Path Following ◽  
Close Approach ◽  
Optimal Level ◽  
Singularity Method ◽  
Constant Rate ◽  
Robot Wrist ◽  
Serial Robot ◽  
Tool Position ◽  
Virtual Joints

Abstract Adjusting the displacement path of a serial robot encountering the wrist singularity to pass either through the singularity or around it mitigates its adverse effects. Both such path adjustments are commonly called singularity avoidance and are applied here to either a spherical or an offset wrist. These adjustments avoid high joint rates that can occur at singularity encounter. A recent through-the singularity method limits joint rates and accelerations in the robot with either a spherical or offset wrist when conducting a constant rate of traversal of the tool manipulated by the robot. A kinematic model adding multiple virtual joints allows a modified high-order path-following algorithm to maintain accurate tool position while achieving an optimal level of tool deviation in orientation. Whereas a path reversal resulting from a turning-point type singularity had been revealed for an offset wrist over a finite range of close-approach, these conditions are met when connecting the isolated path segments. Procedures are developed here with this capability for an around-the-singularity path. Choosing between the through and around-singularity alternatives offers the overall optimum.

scholarly journals Optimal path crossing the orientation exclusion zone of a robot with offset wrist

Robotica ◽  
2021 ◽  
pp. 1-22
Author(s):  
Paul Milenkovic
Keyword(s):  
Small Deviation ◽  
Optimal Path ◽  
Kinematic Model ◽  
Path Following ◽  
Maximum Deviation ◽  
Exclusion Zone ◽  
Step Size ◽  
Spherical Wrist ◽  
Serial Robot ◽  
Control Step

Abstract An unexpected path reversal is discovered for a serial robot with an offset-axis wrist over a finite range of proximity to the wrist singularity. This is replicated by a kinematic model. A prior spherical-wrist method transits the singularity with limited joint rate and acceleration under a constant rate of tool traversal. Accurate position is maintained by controlling a small deviation in orientation. Extensions to the method for an offset wrist (1) find the least-maximum deviation, (2) identify and locate where a path reversal occurs, and (3) use this point to control step size in a high-order predictor-correction path following procedure.

scholarly journals Kinematics of Serial Manipulators

2020 ◽  
Author(s):  
Ivan Virgala ◽  
Michal Kelemen ◽  
Erik Prada
Keyword(s):  
Rigid Body ◽  
Numerical Solutions ◽  
Kinematic Model ◽  
Inverse Kinematic ◽  
Body Motion ◽  
Robot Kinematics ◽  
Kinematic Modeling ◽  
Open Chain ◽  
Serial Manipulators ◽  
Serial Robot

This book chapter deals with kinematic modeling of serial robot manipulators (open-chain multibody systems) with focus on forward as well as inverse kinematic model. At first, the chapter describes basic important definitions in the area of manipulators kinematics. Subsequently, the rigid body motion is presented and basic mathematical apparatus is introduced. Based on rigid body conventions, the forward kinematic model is established including one of the most used approaches in robot kinematics, namely the Denavit-Hartenberg convention. The last section of the chapter analyzes inverse kinematic modeling including analytical, geometrical, and numerical solutions. The chapter offers several examples of serial manipulators with its mathematical solution.

Path Following for the Soft Origami Crawling Robot

2019 ◽  
Author(s):  
Oyuna Angatkina ◽  
Kimberly Gustafson ◽  
Aimy Wissa ◽  
Andrew Alleyne
Keyword(s):  
Autonomous Navigation ◽  
Degrees Of Freedom ◽  
Kinematic Model ◽  
Path Following ◽  
Search And Rescue ◽  
Soft Robots ◽  
Path Following Control ◽  
Straight Line ◽  
Pure Pursuit ◽  
Extensive Growth

Abstract Extensive growth of the soft robotics field has made possible the application of soft mobile robots for real world tasks such as search and rescue missions. Soft robots provide safer interactions with humans when compared to traditional rigid robots. Additionally, soft robots often contain more degrees of freedom than rigid ones, which can be beneficial for applications where increased mobility is needed. However, the limited number of studies for the autonomous navigation of soft robots currently restricts their application for missions such as search and rescue. This paper presents a path following technique for a compliant origami crawling robot. The path following control adapts the well-known pure pursuit method to account for the geometric and mobility constraints of the robot. The robot motion is described by a kinematic model that transforms the outputs of the pure pursuit into the servo input rotations for the robot. This model consists of two integrated sub-models: a lumped kinematic model and a segmented kinematic model. The performance of the path following approach is demonstrated for a straight-line following simulation with initial offset. Finally, a feedback controller is designed to account for terrain or mission uncertainties.

scholarly journals Closed-loop control of soft continuum manipulators under tip follower actuation

2021 ◽  
pp. 027836492199716
Author(s):  
Federico Campisano ◽  
Simone Caló ◽  
Andria A. Remirez ◽  
James H. Chandler ◽  
Keith L. Obstein ◽  
...  
Keyword(s):  
Closed Loop ◽  
Kinematic Model ◽  
Path Following ◽  
External Loading ◽  
Closed Loop Control ◽  
Loop Control ◽  
Actuation System ◽  
Control Scheme ◽  
Continuum Manipulators ◽  
Continuum Manipulator

Continuum manipulators, inspired by nature, have drawn significant interest within the robotics community. They can facilitate motion within complex environments where traditional rigid robots may be ineffective, while maintaining a reasonable degree of precision. Soft continuum manipulators have emerged as a growing subfield of continuum robotics, with promise for applications requiring high compliance, including certain medical procedures. This has driven demand for new control schemes designed to precisely control these highly flexible manipulators, whose kinematics may be sensitive to external loads, such as gravity. This article presents one such approach, utilizing a rapidly computed kinematic model based on Cosserat rod theory, coupled with sensor feedback to facilitate closed-loop control, for a soft continuum manipulator under tip follower actuation and external loading. This approach is suited to soft manipulators undergoing quasi-static deployment, where actuators apply a follower wrench (i.e., one that is in a constant body frame direction regardless of robot configuration) anywhere along the continuum structure, as can be done in water-jet propulsion. In this article we apply the framework specifically to a tip actuated soft continuum manipulator. The proposed control scheme employs both actuator feedback and pose feedback. The actuator feedback is utilized to both regulate the follower load and to compensate for non-linearities of the actuation system that can introduce kinematic model error. Pose feedback is required to maintain accurate path following. Experimental results demonstrate successful path following with the closed-loop control scheme, with significant performance improvements gained through the use of sensor feedback when compared with the open-loop case.

An improved kinematic model for serial robot calibration based on local POE formula using position measurement

2018 ◽  
Vol 45 (5) ◽  
pp. 573-584 ◽  
Author(s):  
Hua Liu ◽  
Weidong Zhu ◽  
Huiyue Dong ◽  
Yinglin Ke
Keyword(s):  
Kinematic Model ◽  
Calibration Model ◽  
Drilling Machine ◽  
Kinematic Calibration ◽  
Position Measurement ◽  
Robot Calibration ◽  
Positioning Accuracy ◽  
Content Type ◽  
Proposed Model ◽  
Serial Robot

Purpose This paper aims to propose a calibration model for kinematic parameters identification of serial robot to improve its positioning accuracy, which only requires position measurement of the end-effector. Design/methodology/approach The proposed model is established based on local frame representation of the product of exponentials (local POE) formula, which integrates all kinematic errors into the twist coordinates errors; then they are identified with the tool frame’ position deviations simultaneously by an iterative least squares algorithm. Findings To verify the effectiveness of the proposed method, extensive simulations and calibration experiments have been conducted on a 4DOF SCARA robot and a 5DOF drilling machine, respectively. The results indicate that the proposed model outperforms the existing model in convergence, accuracy, robustness and efficiency; fewer measurements are needed to gain an acceptable identification result. Practical implications This calibration method has been applied to a variable-radius circumferential drilling machine. The machine’s positioning accuracy can be significantly improved from 11.153 initially to 0.301 mm, which is well in the tolerance (±0.5 mm) for fastener hole drilling in aircraft assembly. Originality/value An accurate and efficient kinematic calibration model has been proposed, which satisfies the completeness, continuity and minimality requirements. Due to generality, this model can be widely used for serial robot kinematic calibration with any combination of revolute and prismatic joints.

scholarly journals Experimental Analysis on the Effectiveness of Kinematic Error Compensation Methods for Serial Industrial Robots

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Ying Zhang ◽  
Guifang Qiao ◽  
Guangming Song ◽  
Aiguo Song ◽  
Xiulan Wen
Keyword(s):  
Error Compensation ◽  
Kinematic Model ◽  
Compensation Method ◽  
Industrial Robots ◽  
Identification Accuracy ◽  
Kinematic Error ◽  
Robot Calibration ◽  
Experiment Platform ◽  
Compensation Methods ◽  
Serial Robot

Based on the established serial 6-DOF robot calibration experiment platform, this paper aims to analyze and compare the effects of four error compensation methods, which are pseudotarget iteration-based error compensation method with three different forms and the Newton–Raphson-based error compensation method. Firstly, the pose error model of the serial robot is established based on the M-DH model in this paper. The calibration results show that the accuracy of the Staubli TX60 robot has been greatly improved. The average comprehensive position accuracy is increased by 88.7%, and the average comprehensive attitude accuracy is increased by 56.6%. Secondly, the principles of the four error compensation methods are discussed, and the effectiveness of the four error compensation methods are compared through experiments. The results show that the four error compensation methods can achieve error compensation well. The compensation accuracy is consistent with the identification accuracy of the kinematic model. The pseudotarget iteration with differential form has the best performance by the comprehensive consideration of accuracy and computational efficiency. Error compensation determines whether the accuracy of the identified model can be achieved. This paper presents a systematic experimental validation research on the effectiveness of four error compensation methods, which provides a reliable reference for the kinematic error compensation of industrial robots.

Noise sensitivity of selected kinematic path following controllers for a unicycle

2014 ◽  
Vol 62 (1) ◽  
pp. 3-13
Author(s):  
U. Libal ◽  
J. Płaskonka
Keyword(s):  
Mobile Robot ◽  
Kinematic Model ◽  
Path Following ◽  
Noise Sensitivity ◽  
Control Algorithms ◽  
Statistical Techniques ◽  
Frenet Frame ◽  
State Variables ◽  
Kinematic Control ◽  
The One

Abstract In the paper a path following problem for a wheeled mobile robot of (2,0) type has been considered. The kinematic model of the robot was derived with respect to the Serret-Frenet frame. Two kinematic control algorithms - Samson and Morin-Samson - have been tested taking into account their sensitivity to a white noise with a zero mean appearing in the one of state variables. The properties of path following errors have been analysed using statistical techniques. The conclusions related to an acceptable level of noise and a range of applicability of the presented algorithms have been reached.

scholarly journals High-speed path following control of skid-steered vehicles

2019 ◽  
Vol 38 (9) ◽  
pp. 1124-1148 ◽  
Author(s):  
Goran Huskić ◽  
Sebastian Buck ◽  
Matthieu Herrb ◽  
Simon Lacroix ◽  
Andreas Zell
Keyword(s):  
High Speed ◽  
Actuator Saturation ◽  
Kinematic Model ◽  
Path Following ◽  
Lyapunov Theory ◽  
Path Following Control ◽  
Control Scheme ◽  
Combined Solution ◽  
Nonlinear Control Law ◽  
Following Error

We present a robust control scheme for skid-steered vehicles that enables high-speed path following on challenging terrains. First, a kinematic model with experimentally identified parameters is constructed to describe the terrain-dependent motion of skid-steered vehicles. Using Lyapunov theory, a nonlinear control law is defined, guaranteeing the convergence of the vehicle to the path. To allow smooth and accurate motion at higher speeds, an additional linear velocity control scheme is proposed, which takes actuator saturation, path following error, and reachable curvatures into account. The combined solution is experimentally evaluated and compared against two state-of-the-art algorithms, by using two different robots on several different terrain types, at different speeds. A Robotnik Summit XL robot is tested on three different terrain types and two different paths at speeds up to [Formula: see text] m/s. A Segway RMP 440 robot is tested on three different terrain types and two different path types at speeds up to [Formula: see text] m/s.

The Research of Rapid Construction Method of Kinematics Coordinate System from a Kind of Mobile Robot

2014 ◽  
Vol 721 ◽  
pp. 299-302
Author(s):  
Chen Hua Lu ◽  
Meng Jun Song
Keyword(s):  
Mobile Robot ◽  
Coordinate System ◽  
Kinematic Model ◽  
Construction Method ◽  
Robot Kinematics ◽  
Rapid Construction ◽  
Serial Robot

In order to study how to solve the serial robot kinematics quickly, so we transformed the kinematics coordinate system by Y axis, and the computed results show that transforming the kinematics coordinate system by Y axis could solve the kinematic model quickly and efficiently; the computed results suggest that constructing the redundant coordinate system and transforming the kinematics coordinate system by Y axis could solve the serial robotic kinematics efficiently.

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