scholarly journals A Novel Virtual Sensor for Estimating Robot Joint Total Friction Based on Total Momentum

2019 ◽  
Vol 9 (16) ◽  
pp. 3344 ◽  
Author(s):  
Xu ◽  
Fan ◽  
Fang ◽  
Wang ◽  
Zhu ◽  
...  
Keyword(s):  
Performance Improvement ◽  
Trajectory Tracking ◽  
Friction Model ◽  
Friction Torque ◽  
Joint Torque ◽  
Tracking Performance ◽  
Step Response ◽  
Virtual Sensor ◽  
Joint Friction ◽  
Velocity Tracking

Robot joint friction is an important and complicated issue in improving robot control performance. In this paper, a virtual sensor based on the total generalized momentum concept is proposed to estimate the total friction torque, including both the motor-side and link-side friction, of robot joints without joint torque sensors. The proposed algorithm only requires a robot joint dynamics model and not a complex friction model dependent on factors such as time and velocity. By compensating for the estimated friction torque with a robot joint controller, the trajectory tracking performance of the controller, especially the velocity tracking performance, can be improved. To verify the effectiveness of the developed algorithm, 2-DOF planar manipulator simulations and single-joint system experiments are conducted. The simulation and experimental results show that the designed virtual sensor can effectively estimate the total joint friction disturbance and that the controller trajectory tracking performance is improved after observed friction compensation. However, the position tracking performance improvement of the controller is less than that for the velocity tracking performance improvement during the experiments. In addition, the velocity step response ability and velocity tracking performance of the controller are improved more at low velocities than that at high velocities in the experiments. The proposed algorithm has engineering and theoretical significance for estimating robot joint friction and improving the performance of robot joint controllers.

Static Analysis of Spherical nR Kinematic Chains With Joint Friction

1992 ◽  
Author(s):  
Pierre Larochelle ◽  
J. M. McCarthy
Keyword(s):  
Static Analysis ◽  
Bending Moment ◽  
Iterative Solution ◽  
Friction Model ◽  
Friction Torque ◽  
Force Balance ◽  
External Loading ◽  
Linear System Of Equations ◽  
Kinematic Chains ◽  
Joint Friction

Abstract This paper presents the static analysis of general spherical nR simple open or closed kinematic chains with joint friction. The internal loading on each link is found to consist of a bending moment and a torsional moment. The goal of this analysis is to determine these moments which are then used in designing the link. The moment and force balance equations for each link yields a linear system of equations which define the internal moments of the mechanism and the output torque on the driven crank for a given input torque. A Coulomb model of joint friction is used to determine the friction torque along the axis of a joint. The joint friction model requires an iterative solution. The purpose of this algorithm is to provide a means of computing the complete internal and external loading on the members of spherical chains while including frictional effects in order to facilitate the design of a functional spherical mechanisms.

Trajectory and Vibration Control of a Single-Link Flexible-Joint Manipulator Using a Distributed Higher-Order Differential Feedback Controller

2017 ◽  
Vol 139 (8) ◽  
Author(s):  
John T. Agee ◽  
Zafer Bingul ◽  
Selcuk Kizir
Keyword(s):  
Trajectory Tracking ◽  
Higher Order ◽  
Feedback Controller ◽  
Step Response ◽  
Position Measurement ◽  
Tracking Errors ◽  
Flexible Joint ◽  
Nonminimum Phase ◽  
Step Input ◽  
Flexible Joint Manipulator

The trajectory tracking in the flexible-joint manipulator (FJM) system becomes complicated since the flexibility of the joint of the FJM superimposes vibrations and nonminimum phase characteristics. In this paper, a distributed higher-order differential feedback controller (DHODFC) using the link and joint position measurement was developed to reduce joint vibration in step input response and to improve tracking behavior in reference trajectory tracking control. In contrast to the classical higher-order differential (HOD), the dynamics of the joint and link are considered separately in DHODFC. In order to validate the performance of the DHODFC, step input, trajectory tracking, and disturbance rejection experiments are conducted. In order to illustrate the differences between classical HOD and DHODFC, the performance of these controllers is compared based on tracking errors and energy of control signal in the tracking experiments and fundamental dynamic characteristics in the step response experiments. DHODFC produces better tracking errors with almost same control effort in the reference tracking experiments and a faster settling time, less or no overshoot, and higher robustness in the step input experiments. Dynamic behavior of DHODFC is examined in continuous and discontinues inputs. The experimental results showed that the DHODFC is successful in the elimination of the nonminimum phase dynamics, reducing overshoots in the tracking of such discontinuous input trajectories as step and square waveforms and the rapid damping of joint vibrations.

On the Application of the Lu-Gre Model to Simulate Joint Friction in Multi-Body Systems

2011 ◽  
Author(s):  
Kedar Gajanan Kale ◽  
Rajiv Rampalli
Keyword(s):  
Friction Model ◽  
Lugre Model ◽  
Friction Forces ◽  
Joint Friction ◽  
Modeling Techniques ◽  
Static Regime ◽  
Increasing Demand ◽  
Automotive Suspension ◽  
Multi Body

Advances in the application of multi-body simulation technology to real world problems have led to an ever increasing demand for higher fidelity modeling techniques. Of these, accurate modeling of friction is of strategic interest in applications such as control system design, automotive suspension analysis, robotics etc. Joints (sometimes referred to as constraints) play an important role in defining the dynamics of a multi-body system. Hence, it is imperative to accurately account for friction forces arising at these joints due to the underlying interface dynamics. In this paper, we discuss the application of LuGre, a dynamic friction model to simulate joint friction. We choose the LuGre model due to its ability to capture important effects such as the Stribeck effect and the Dahl effect. The native 1-d LuGre model is extended to formulate friction computations for non-trivial joint geometries and dynamics in 2 and 3 dimensions. It is also extended to work in the quasi-static regime. Specific applications to revolute, cylindrical and spherical joints in multi-body systems are discussed. Finally, an engineering case study on the effects of joint friction in automotive suspension analysis is presented.

Direct Sensitivity Analysis of Spatial Multibody Systems With Joint Friction Using Index-1 Formulation

2021 ◽  
Author(s):  
Adwait Verulkar ◽  
Corina Sandu ◽  
Daniel Dopico ◽  
Adrian Sandu
Keyword(s):  
Sensitivity Analysis ◽  
Dynamic Systems ◽  
Multibody Systems ◽  
Friction Model ◽  
Design Parameters ◽  
Adjoint Sensitivity ◽  
Joint Friction ◽  
Multibody Dynamic ◽  
Model Dynamics ◽  
Direct Sensitivity

Abstract Sensitivity analysis is one of the most prominent gradient based optimization techniques for mechanical systems. Model sensitivities are the derivatives of the generalized coordinates defining the motion of the system in time with respect to the system design parameters. These sensitivities can be calculated using finite differences, but the accuracy and computational inefficiency of this method limits its use. Hence, the methodologies of direct and adjoint sensitivity analysis have gained prominence. Recent research has presented computationally efficient methodologies for both direct and adjoint sensitivity analysis of complex multibody dynamic systems. The contribution of this article is in the development of the mathematical framework for conducting the direct sensitivity analysis of multibody dynamic systems with joint friction using the index-1 formulation. For modeling friction in multibody systems, the Brown and McPhee friction model has been used. This model incorporates the effects of both static and dynamic friction on the model dynamics. A case study has been conducted on a spatial slider-crank mechanism to illustrate the application of this methodology to real-world systems. Using computer models, with and without joint friction, effect of friction on the dynamics and model sensitivities has been demonstrated. The sensitivities of slider velocity have been computed with respect to the design parameters of crank length, rod length, and the parameters defining the friction model. Due to the highly non-linear nature of friction, the model dynamics are more sensitive during the transition phases, where the friction coefficient changes from static to dynamic and vice versa.

Comparison of Motion Characteristics of High Performance CNC Rotary Tables

2010 ◽  
Author(s):  
Muditha K. M. Dassanayake ◽  
Masaomi Tsutsumi
Keyword(s):  
High Performance ◽  
Closed Loop ◽  
Friction Torque ◽  
Step Response ◽  
Rotary Table ◽  
Direct Drive ◽  
Drive Motor ◽  
Fluctuation Frequency ◽  
Motion Characteristics ◽  
Accuracy And Repeatability

In this paper, the motion performances of the two rotary tables which are driven by roller gear cam and direct drive motor are measured and compared. The table with roller gear cam was controlled in semi-closed loop and full-closed loop methods while the other was controlled only in full-closed loop method. In the measurements, the positioning accuracy and repeatability, rotational fluctuation, frequency response, step response and etc of the systems were measured. All these tests were carried out without any kind of compensation methods such as pitch error or cogging torque compensation etc. Three rotary encoders for rotary table with roller gear cam and one rotary encoder for rotary table with direct drive motor were used for measurements. Furthermore, the simulations were carried out by mathematical models and the results were compared with measured results. The comparison shows that the measured and simulated results have a good agreement. From the simulation results, the friction torque was identified and also compared. The results imply that though both the tables show high performances, the performances of the rotary table driven by roller gear cam are comparatively higher than that of rotary table driven by direct drive motor.

scholarly journals Adaptive PD Sliding Mode Control For 4 DOF SCARA Variant

2021 ◽  
Author(s):  
Manjeet Tummalapalli
Keyword(s):  
Sliding Mode Control ◽  
Trajectory Tracking ◽  
High Speed ◽  
Sliding Mode ◽  
Adaptive Controller ◽  
Degree Of Freedom ◽  
Tracking Performance ◽  
Advantages And Disadvantages ◽  
Model Free ◽  
Adaptive Law

This project proposes a new SCARA variant with 4 degree of freedom. The proposed variant is achieved by swapping joint 2 and joint 3 of the standard SCARA robots. An adaptive controller is defined based on the advantages and disadvantages of PD, and SMC controllers.The purpose of the project is to understand the dynamics of the variant and to track the performance for trajectories. Simulations for tracking performance are carried under linear and circular trajectories. The variant is studied over the three controllers; PD, PD-SMC and A-PD-SMC. The variant under the adaptive controller is most efficient in terms of tracking performance and the control inputs to the system. The system is simulated under high speed and with the influence of friction at the joints. The control gains are held constant for both the trajectories and hence the controller is able to perform good under changing trajectories. Due to the use of the adaptive law, the system is at the ease of implementation and since no priori knowledge if the system is needed, it is model free. Therefore, the proposed adaptive PD-SMC has proven to provide good, robust trajectory tracking.

scholarly journals TRANSMITTED POWER AND ENERGY FLOW BEHAVIOR OF DEGRADING WET FRICTION CLUTCHES

2012 ◽  
pp. 286-291
Author(s):  
SHOAIB IQBAL ◽  
THIERRY JANSSENS ◽  
WIM DESMET ◽  
FARID AL- BENDER
Keyword(s):  
Energy Flow ◽  
Relative Velocity ◽  
Normal Load ◽  
Flow Behavior ◽  
Friction Material ◽  
Friction Model ◽  
Friction Torque ◽  
Phase Changes ◽  
Transmitted Power ◽  
Wet Friction

Experiments and simulations performed in the framework of accelerated-life tests of wet friction clutches reveal that with the progression of degradation of clutches, the transmitted power decreases together with a change in the energy flow behavior, mainly in the pre-lockup phase. In addition, the engagement duration increases and the relative velocity fluctuation in post-lockup phase changes. These degradation effects are due to the reduction in friction torque and the change in the relative velocity profile caused by the changing friction characteristics of the clutch friction material with degradation. Simulations are performed in a bond graph methodology incorporating an adapted form of the Generalized Maxwell Slip (GMS) friction model, which calculates the friction torque taking into account the dynamic variation in relative velocity and the normal load.

Effect of Short-Term Weather Predictions on Model Predictive Trajectory Tracking Performance of Unmanned Surface Vessels

2020 ◽  
Author(s):  
Benjamin Armentor ◽  
Joseph Stevens ◽  
Nathan Madsen ◽  
Andrew Durand ◽  
Joshua Vaughan
Keyword(s):  
Trajectory Tracking ◽  
Wind Waves ◽  
Tracking Error ◽  
Tracking Performance ◽  
Model Predictive Controller ◽  
Prediction Horizon ◽  
Surface Vessels ◽  
Waves And Currents ◽  
Predictive Controller ◽  
Disturbance Model

Abstract For mobile robots, such as Autonomous Surface Vessels (ASVs), limiting error from a target trajectory is necessary for effective and safe operation. This can be difficult when subjected to environmental disturbances like wind, waves, and currents. This work compares the tracking performance of an ASV using a Model Predictive Controller that includes a model of these disturbances. Two disturbance models are compared. One prediction model assumes the current disturbance measurements are constant over the entire prediction horizon. The other uses a statistical model of the disturbances over the prediction horizon. The Model Predictive Controller performance is also compared to a PI-controlled system under the same disturbance conditions. Including a disturbance model in the prediction of the dynamics decreases the trajectory tracking error over the entire disturbance spectrum, especially for longer horizon lengths.

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