scholarly journals Design and Calibration of Robot Base Force/Torque Sensors and Their Application to Non-Collocated Admittance Control for Automated Tool Changing

Sensors ◽  
2021 ◽  
Vol 21 (9) ◽  
pp. 2895
Author(s):  
Hubert Gattringer ◽  
Andreas Müller ◽  
Philip Hoermandinger
Keyword(s):  
Steel Plate ◽  
Robotic Manipulators ◽  
Indirect Measurement ◽  
Local Deformation ◽  
Contact Forces ◽  
The Novel ◽  
Admittance Control ◽  
Load Cells ◽  
Series Elastic Actuators ◽  
Automated Tool

Robotic manipulators physically interacting with their environment must be able to measure contact forces/torques. The standard approach to this end is attaching force/torque sensors directly at the end-effector (EE). This provides accurate measurements, but at a significant cost. Indirect measurement of the EE-loads by means of torque sensors at the actuated joint of a robot is an alternative, in particular for series-elastic actuators, but requires dedicated robot designs and significantly increases costs. In this paper, two alternative sensor concept for indirect measurement of EE-loads are presented. Both sensors are located at the robot base. The first sensor design involves three load cells on which the robot is mounted. The second concept consists of a steel plate with four spokes, at which it is suspended. At each spoke, strain gauges are attached to measure the local deformation, which is related to the load at the sensor plate (resembling the main principle of a force/torque sensor). Inferring the EE-load from the so determined base wrench necessitates a dynamic model of the robot, which accounts for the static as well as dynamic loads. A prototype implementation of both concepts is reported. Special attention is given to the model-based calibration, which is crucial for these indirect measurement concepts. Experimental results are shown when the novel sensors are employed for a tool changing task, which to some extend resembles the well-known peg-in-the-hole problem.

scholarly journals A Coefficient Diagram Method Controller with Backstepping Methodology for Robotic Manipulators

2015 ◽  
Vol 66 (5) ◽  
pp. 270-276 ◽  
Author(s):  
Fouad Haouari ◽  
Bali Nourdine ◽  
Mohamed Segir Boucherit ◽  
Mohamed Tadjine
Keyword(s):  
Robotic Manipulators ◽  
Control Law ◽  
Control Procedure ◽  
Parametric Uncertainties ◽  
The Novel ◽  
External Disturbances ◽  
Diagram Method ◽  
Coefficient Diagram Method ◽  
Backstepping Controller ◽  
Puma Robot

AbstractA new robust control procedure for robot manipulators is proposed in this paper. Coefficients diagram method controllers CDM and Backstepping methodology are combined to create the novel control law. Two steps of backstepping on the resulting system are used to design a nonlinear CDM-Backstepping controller. Simulations on a PUMA robot including external disturbances, parametric uncertainties and noises are performed to show the effectiveness and feasibility of the proposed method.

Mathematical models for indirect measurement of contact forces in hexagonal idler housing of pipe conveyor

Measurement ◽  
2014 ◽  
Vol 47 ◽  
pp. 794-803 ◽  
Author(s):  
Vieroslav Molnár ◽  
Gabriel Fedorko ◽  
Beáta Stehlíková ◽  
Peter Michalik ◽  
Melichar Kopas
Keyword(s):  
Mathematical Models ◽  
Indirect Measurement ◽  
Contact Forces

An Extraction Method Based on Invariance Geometric Feature

2015 ◽  
Vol 713-715 ◽  
pp. 1570-1573
Author(s):  
Rong Fen Gong ◽  
Mao Xiang Chu ◽  
Yong Hui Yang
Keyword(s):  
Extraction Method ◽  
Steel Plate ◽  
The Other ◽  
Geometric Feature ◽  
Geometric Features ◽  
The Novel ◽  
Statistical Features ◽  
Plate Surface ◽  
Shape Features ◽  
Defects Classification

An extraction method based on invariance geometric feature is proposed in this paper. This method extracts two types of feature from the object in an image. One type is five invariance statistical features of edge distance. The other is two invariance shape features: rectangular similarity feature and circular similarity feature. Moreover, this proposed method is used to extract defect features for steel plate surface. Its performance is tested in scale and rotation invariance and defects classification. Experimental results show that the novel geometric features have the ability of invariance and can improve the accuracy of classification.

Walk-through programming for robotic manipulators based on admittance control

Robotica ◽  
2013 ◽  
Vol 31 (7) ◽  
pp. 1143-1153 ◽  
Author(s):  
Luca Bascetta ◽  
Gianni Ferretti ◽  
Gianantonio Magnani ◽  
Paolo Rocco
Keyword(s):  
Robot Control ◽  
Industrial Robot ◽  
Robotic Manipulators ◽  
Programming System ◽  
Admittance Control ◽  
Safety Issues ◽  
Safety Strategies ◽  
Programming Techniques ◽  
Tool Centre Point ◽  
Safety Limit

SUMMARYThe present paper addresses the issues that should be covered in order to develop walk-through programming techniques (i.e. a manual guidance of the robot) in an industrial scenario. First, an exact formulation of the dynamics of the tool the human should feel when interacting with the robot is presented. Then, the paper discusses a way to implement such dynamics on an industrial robot equipped with an open robot control system and a wrist force/torque sensor, as well as the safety issues related to the walk-through programming. In particular, two strategies that make use of admittance control to constrain the robot motion are presented. One slows down the robot when the velocity of the tool centre point exceeds a specified safety limit, the other one limits the robot workspace by way of virtual safety surfaces. Experimental results on a COMAU Smart Six robot are presented, showing the performance of the walk-through programming system endowed with the two proposed safety strategies.

scholarly journals Dynamical Modeling and Control of Modular Snake Robots With Series Elastic Actuators for Pedal Wave Locomotion on Uneven Terrain

2019 ◽  
Vol 142 (3) ◽  
Author(s):  
Mohammadali Javaheri Koopaee ◽  
Christopher Pretty ◽  
Koen Classens ◽  
XiaoQi Chen
Keyword(s):  
Wave Motion ◽  
Vertical Plane ◽  
Contact Forces ◽  
Contact Model ◽  
Lagrange Equations ◽  
Uneven Terrain ◽  
Contact Points ◽  
Series Elastic Actuators ◽  
Snake Robots ◽  
Series Elastic

Abstract This paper introduces the equations of motion of modular 2D snake robots moving in vertical plane employing Series Elastic Actuators (SEAs). The kinematics of such 2D modular snake robot is presented in an efficient matrix form and Euler–Lagrange equations are constructed to model the robot. Moreover, using a spring-damper contact model, external contact forces, necessary for modeling pedal wave motion (undulation in the vertical plane) are taken into account, which unlike existing methods can be used to model the effect of multiple contact points. Using such a contact model, pedal wave motion of the robot is simulated and the torque signal measured by the elastic element from the simulation and experimentation are used to show the validity of the model. Moreover, pedal wave locomotion of such robot on uneven terrain is also modeled and an adaptive controller based on torque feedback in gait parameter's space with optimized control gain is proposed. The simulation and experimentation results showed the efficacy of the proposed controller as the robot successfully climbed over a stair-type obstacle without any prior knowledge about its location with at least 24.8% higher speed compared with non-adaptive motion.

Virtual Coupling Based Control Methodology for Lower Extremity Exoskeleton

2014 ◽  
Vol 556-562 ◽  
pp. 2365-2369 ◽  
Author(s):  
Jin Xiang Cui ◽  
Yan He Zhu ◽  
Ben Zhou Xu
Keyword(s):  
Lower Extremity ◽  
Control Strategy ◽  
Degrees Of Freedom ◽  
Virtual Prototype ◽  
Contact Forces ◽  
Admittance Control ◽  
Collaborative Simulation ◽  
Virtual Coupling ◽  
Control Methodology ◽  
Positional Control

As one of the most important examples of human-orientated system, the exoskeleton can improve the strength and endurance of the wearer. The exoskeleton has multi-degrees of freedom. As a result, a stable controller for the exoskeleton is difficult to design. The adoption of a purely positional control strategy may lead to large contact forces. Hence, an admittance control strategy is devised aimed at limiting both internal and contact forces. To verify the rationality and feasibility of the control strategy, we introduce a method utilizing virtual prototype and collaborative simulation.

Modeling and Error Analysis of Hydrodynamic Experimental Apparatus

2014 ◽  
Vol 621 ◽  
pp. 456-461
Author(s):  
Yang Wei Wang ◽  
Kai Yu ◽  
Jin Bo Tan
Keyword(s):  
Measurement Accuracy ◽  
Three Dimensional ◽  
Measurement Data ◽  
The Novel ◽  
Mechanical Structure ◽  
Experimental Apparatus ◽  
Load Cells ◽  
Experiment Subject ◽  
Hydrodynamic Experiment ◽  
The Relationship

A hydrodynamic experiment apparatus is constructed to accomplish the measurement of hydrodynamic force on three-dimensional. This paper firstly introduces the mechanical structure of the novel hydrodynamic experiment apparatus. Then, it introduces the mathematical modeling of the hydrodynamic experiment apparatus which is based on the relationship between measurement data and the force on experiment subject. Finally, the error source of the mechanical structure and load cells were analyzed and the error compensation model is established to improve the measurement accuracy.

Contact Forces Acting on Large Femoral Osteochondral Allografts During Forced Knee Extension

2017 ◽  
Vol 45 (12) ◽  
pp. 2804-2811 ◽  
Author(s):  
Peter Z. Du ◽  
Keith L. Markolf ◽  
Christopher J. Lama ◽  
David R. McAllister ◽  
Kristofer J. Jones
Keyword(s):  
Clinical Relevance ◽  
Knee Extension ◽  
Load Cell ◽  
Contact Forces ◽  
Osteochondral Allograft ◽  
Human Knee ◽  
Native Bone ◽  
Load Cells ◽  
The Mean ◽  
Femoral Condyles

Background: A single cylindrical graft plug is commonly used for large focal femoral defects during osteochondral allograft (OCA) transplantation. Excessive contact force (CF) on a proud plug could compromise initial healing. CFs during forced knee extension are of particular interest because this maneuver is used by therapists to restore early postoperative range of motion. Hypothesis: A proud OCA plug will significantly increase the CF and significantly decrease the knee extension angle (KEA). Study Design: Controlled laboratory study. Methods: Eleven human knee specimens had miniature load cells installed in both femoral condyles at standardized locations representative of clinical defects. Each load cell had a 20-mm–diameter cylinder of native bone/cartilage attached at its precise anatomic location. Four spacers, 0.5 mm in thickness, were inserted sequentially between each load cell and its mounting bracket to create proud plug conditions of 0.5 to 2 mm. Measurements of the CF and KEA were recorded at extension moment levels up to 8 N·m. Results: At 8 N·m, the mean CFs for flush plugs were 149 ± 18 N (lateral) and 34 ± 13 N (medial). The mean increases in the medial CF (compared with flush) for 0.5-mm, 1-mm, 1.5-mm, and 2-mm proud conditions were 31 N (+91%), 64 N (+188%), 111 N (+325%), and 154 N (+451%), respectively. Corresponding increases for lateral proud plugs were 55 N (+37%), 120 N (+81%), 162 N (+109%), and 210 N (+141%), respectively. The CFs (and CF increases) for lateral grafts were significantly ( P < .05) higher than corresponding values for medial grafts at each proudness condition. Medial plug proudness had no consistent effect on the KEA. A 1-mm proud lateral plug significantly reduced the KEA by −1.6° (0 N·m) and −0.9° (2 N·m). Conclusion: Graft proudness of only 0.5 mm significantly increased CFs during forced knee extension, emphasizing the surgical precision necessary to achieve normal CF levels. Clinical Relevance: It is believed that some amount of CF is beneficial in the early stages of graft healing, and our findings suggest that forced knee extension may be well suited for this purpose. However, the surgeon should be aware that large extension moments can also generate relatively high CFs, especially if the plug is proud.

Shape Sensing for Soft Robotic Manipulators

2009 ◽  
Author(s):  
Deepak Trivedi ◽  
Christopher D. Rahn
Keyword(s):  
Degrees Of Freedom ◽  
Soft Materials ◽  
Robotic Manipulators ◽  
Sensors And Actuators ◽  
Backbone Curve ◽  
Continuum Robots ◽  
Soft Robots ◽  
Load Cells ◽  
Simulation Results ◽  
Shape Sensing

Soft robotic manipulators are continuum robots made of soft materials that undergo continuous elastic deformation and produce motion with a smooth backbone curve. These manipulators offer significant advantages over traditional manipulators due to their ability to conform to their surroundings, move with dexterity and manipulate objects of widely varying size using whole arm manipulation. Theoretically, soft robots have infinite degrees of freedom (dof), but the number of sensors and actuators are limited. Many dofs of soft robots are not directly observable and/or controllable, complicating shape sensing and controlling. In this paper, we present two methods of shape sensing for soft robotic manipulators based on a geometrically exact mechanical model. The first method use s load cells mounted at the base of the manipulator and the second method makes use of cable encoders running through the length of the manipulator. Simulation results show an endpoint localization error of less than 3% of manipulator length.

The Effect of Position and Path Repeatability on Biomechanical Testing of Diarthrodial Joints

2003 ◽  
Author(s):  
Shon P. Darcy ◽  
Jorge E. Gil ◽  
Savio L.-Y. Woo ◽  
Richard E. Debski
Keyword(s):  
Cruciate Ligament ◽  
Biomechanical Testing ◽  
Robotic Manipulators ◽  
Contact Forces ◽  
External Loading ◽  
Diarthrodial Joints ◽  
Payload Capacity ◽  
Joint Contact ◽  
High Payload

To improve surgical procedures and rehabilitation protocols for injuries to the anterior cruciate ligament (ACL), the function of the ACL and ACL graft during in vivo activities must be understood. Robotic manipulators with a payload less than 500 N (low-payload) have been used to study joint and ligament function during application of external loading conditions (Fujie, 1993; Fujie, 2000). Robotic manipulators with a payload capacity of at least 1500 N (high-payload) will be needed to simulate high joint contact forces that have been estimated to be between 2 to 5 times body weight (Morrison, 1970; Escamilla, 1998). However, there is a trade-off between payload capacity and position and path repeatability. The objective of this study was to determine the effect of position and path repeatability of two high-payload robotic manipulators, (KUKA™ KR210 and FANUC™ S900W) used to apply external loads to diarthrodial joints and determine the corresponding joint kinematics and forces in the soft tissue structures.

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