scholarly journals A Clamping Force Estimation Method Based on a Joint Torque Disturbance Observer Using PSO-BPNN for Cable-Driven Surgical Robot End-Effectors

Sensors ◽  
2019 ◽  
Vol 19 (23) ◽  
pp. 5291 ◽  
Author(s):  
Zhengyu Wang ◽  
Daoming Wang ◽  
Bing Chen ◽  
Lingtao Yu ◽  
Jun Qian ◽  
...  
Keyword(s):  
Disturbance Observer ◽  
Estimation Method ◽  
Surgical Robot ◽  
Joint Torque ◽  
Force Sensing ◽  
Clamping Force ◽  
Force Estimation ◽  
Cable Tension ◽  
One Dimensional ◽  
End Effectors

The ability to sense external force is an important technique for force feedback, haptics and safe interaction control in minimally-invasive surgical robots (MISRs). Moreover, this ability plays a significant role in the restricting refined surgical operations. The wrist joints of surgical robot end-effectors are usually actuated by several long-distance wire cables. Its two forceps are each actuated by two cables. The scope of force sensing includes multidimensional external force and one-dimensional clamping force. This paper focuses on one-dimensional clamping force sensing method that do not require any internal force sensor integrated in the end-effector’s forceps. A new clamping force estimation method is proposed based on a joint torque disturbance observer (JTDO) for a cable-driven surgical robot end-effector. The JTDO essentially considers the variations in cable tension between the actual cable tension and the estimated cable tension using a Particle Swarm Optimization Back Propagation Neural Network (PSO-BPNN) under free motion. Furthermore, a clamping force estimator is proposed based on the forceps’ JTDO and their mechanical relations. According to comparative analyses in experimental studies, the detection resolutions of collision force and clamping force were 0.11 N. The experimental results verify the feasibility and effectiveness of the proposed clamping force sensing method.

scholarly journals Research on micromanipulator’s clamping force sensing based on static wirerope tension of a surgical robot

2015 ◽  
Vol 7 (4) ◽  
pp. 168781401558124 ◽  
Author(s):  
Lingtao Yu ◽  
Zhengyu Wang ◽  
Wenjie Wang ◽  
Hongwei Li ◽  
Lan Wang
Keyword(s):  
Surgical Robot ◽  
Force Sensing ◽  
Clamping Force

scholarly journals A learning-based tip contact force estimation method for tendon-driven continuum manipulator

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Fan Feng ◽  
Wuzhou Hong ◽  
Le Xie
Keyword(s):  
Neural Network ◽  
Contact Force ◽  
Recurrent Neural Network ◽  
Estimation Method ◽  
Training Data ◽  
Force Sensing ◽  
Force Estimation ◽  
Advantages And Disadvantages ◽  
Continuum Manipulator ◽  
Three Degree Of Freedom

AbstractAlthough tendon-driven continuum manipulators have been extensively researched, how to realize tip contact force sensing in a more general and efficient way without increasing the diameter is still a challenge. Rather than use a complex modeling approach, this paper proposes a general tip contact force-sensing method based on a recurrent neural network that takes the tendons’ position and tension as the input of a recurrent neural network and the tip contact force of the continuum manipulator as the output and fits this static model by means of machine learning so that it may be used as a real-time contact force estimator. We also designed and built a corresponding three-degree-of-freedom contact force data acquisition platform based on the structure of a continuum manipulator designed in our previous studies. After obtaining training data, we built and compared the performances of a multi-layer perceptron-based contact force estimator as a baseline and three typical recurrent neural network-based contact force estimators through TensorFlow framework to verify the feasibility of this method. We also proposed a manually decoupled sub-estimators algorithm and evaluated the advantages and disadvantages of those two methods.

scholarly journals Toward force detection of a cable-driven micromanipulator for a surgical robot based on disturbance observer

2017 ◽  
Vol 8 (2) ◽  
pp. 323-335
Author(s):  
Wenjie Wang ◽  
Lingtao Yu ◽  
Jing Yang
Keyword(s):  
Minimally Invasive ◽  
External Force ◽  
Disturbance Observer ◽  
Joint Angle ◽  
Surgical Robot ◽  
Force Sensing ◽  
Average Error ◽  
Feedback Signal ◽  
Loop Control ◽  
Tissue Properties

Abstract. Force sensing plays an important role in minimally invasive surgery (MIS). Force sensing makes it possible for the surgeon to feel the tissue properties and apply an appropriate level force and avoid tissue damage. The micromanipulators are compact and to allow appropriate disinfection, it is inappropriate to integrate sensors at the end of the micromanipulator. In this study, a new asymmetric cable-driven type of micromanipulator for a surgical robot was designed, and a joint angle estimator (JAE) was designed based on the dynamical model of the single cable-driven joint. Closed-loop control of the joint angle was carried out by regarding the JAE output as the feedback signal. On this basis, an external force estimator was designed using a disturbance observer (DOB). The experimental results show an average accuracy of the joint angle estimator of about −0.150°, with excellent control precision, the largest absolute error of about 0.95°, and an average error of 0.175°. The accuracy of the force estimator was at a high level during static loading. The estimated accuracy was 94 % at external force is greater than 1 N, and the estimated accuracy was 82 % for an external force of 0.3 N. These results predict that force sensing of a cable-driven micromanipulator in this paper can used to realize the micromanipulator's force feedback of a minimally invasive surgical robot.

Sliding Perturbation Observer Based Reaction Force Estimation Method of Surgical Robot Instrument for Haptic Realization

2015 ◽  
Vol 12 (02) ◽  
pp. 1550013 ◽  
Author(s):  
Sung Min Yoon ◽  
Min Cheol Lee ◽  
Chi Yen Kim
Keyword(s):  
Coulomb Friction ◽  
Sliding Mode ◽  
Reaction Force ◽  
Estimation Method ◽  
Surgical Robot ◽  
Model Parameters ◽  
Force Estimation ◽  
Haptic Information ◽  
Robust Controller ◽  
Practice Time

Previous research applied sliding mode control with a sliding perturbation observer (SMCSPO) algorithm as a robust controller to control a surgical robotic instrument and reported that reaction force loaded on the tip can be estimated similarly by the sliding perturbation observer (SPO). However, some factors, such as friction, in which it is difficult to find the model parameters beforehand, can have an effect on the reaction force estimation because the factors are included in the estimated perturbation. This paper addresses the SPO based reaction force estimation method to extract a pure reaction force on a surgical robot instrument in the case of including Coulomb friction due to the operation of cable-pulley structure. Coulomb friction can be estimated experimentally and compensated for from the estimated perturbation. An experimental evaluation was performed to prove the suggested estimation method. The results show that SPO can be substituted for sensors to measure the reaction force. This estimated reaction force will be used to realize the haptic function by sending the reaction force to a master device for a surgeon. The results will help to create surgical benefit such as shortening the practice time of a surgeon and providing haptic information to the surgeon by using it as haptic signal to protect an organ by forming a force boundary.

External Force Self-Sensing Based on Cable-Tension Disturbance Observer for Surgical Robot End-Effector

2019 ◽  
Vol 19 (13) ◽  
pp. 5274-5284 ◽  
Author(s):  
Zhengyu Wang ◽  
Bin Zi ◽  
Daoming Wang ◽  
Jun Qian ◽  
Wei You ◽  
...  
Keyword(s):  
External Force ◽  
Disturbance Observer ◽  
Surgical Robot ◽  
Cable Tension ◽  
End Effector

A Redundant Manipulator Joint Torque Estimation Method Based on Disturbance Observer

2020 ◽  
Vol 29 (07n08) ◽  
pp. 2040015
Author(s):  
Xun Liu ◽  
Yaqiu Liu ◽  
Hanchen Zhao
Keyword(s):  
Error Compensation ◽  
Disturbance Observer ◽  
Control Method ◽  
Estimation Method ◽  
Industrial Robots ◽  
Torque Control ◽  
Joint Torque ◽  
Torque Sensor ◽  
Torque Estimation ◽  
Joint Torque Sensor

With the continuous development of the robot industry, both industrial robots and collaborative robots are developing towards light type and intelligence. The core issue is that how to improve the dynamic control performance of robots and reduce costs. The accurate torque feedback control can be achieved by introducing a joint torque sensor. The disadvantages brought by it are higher cost and the limited performance of the torque sensor. Therefore, on the basis of the traditional current estimated torque, combined with the accurate joint torque data fed back by the torque sensor, a method to estimate the harmonic transmission torque in the joint based on the disturbance observer is proposed, and a joint torque model is constructed. At the same time, the compensation factor is introduced to improve the accuracy of torque estimation. In the method proposed in this paper, the theoretical position and actual position, speed difference and motor current of the dual encoder on the motor side and the link side are used to estimate the harmonic transmission torque through the disturbance observer, and the corresponding coefficient is identified. By calibrating the transmission error compensation term and friction force with the torque sensor, the joint torque estimation model is obtained, and the sensorless joint torque estimation can be realized. This method does not require additional torque error compensation caused by harmonic drive deformation in the controller. Therefore, the torque control method without torque sensor is adopted in batch, which is not affected by the configuration and dynamic parameters of the manipulator. In the experiment, the output data of the joint torque sensor is used for testing and comparison. Through the single joint and redundant robot manipulator integration testing, the effectiveness of the proposed joint torque estimation method is verified.

Disturbance-Observer-Based Force Estimation for Haptic Feedback

2010 ◽  
Vol 133 (1) ◽  
Author(s):  
Abhishek Gupta ◽  
Marcia K. O’Malley
Keyword(s):  
Force Control ◽  
Disturbance Observer ◽  
Closed Loop ◽  
Haptic Feedback ◽  
Open Loop ◽  
Contact Forces ◽  
Haptic Interface ◽  
Force Sensing ◽  
Force Estimation ◽  
Control Approach

In this paper, we propose the use of a nonlinear disturbance-observer for estimation of contact forces during haptic interactions. Most commonly used impedance-type haptic interfaces employ open-loop force control under the assumption of pseudostatic interactions. Advanced force control in such interfaces can increase simulation fidelity through improvement of the transparency of the device. However, closed-loop force feedback is limited both due to the bandwidth limitations of force sensing and the associated cost of force sensors required for its implementation. Using a disturbance-observer, we estimate contact forces at the tool tip, then use these estimates for closed-loop control of the haptic interface. Simulation and experimental results, utilizing a custom single degree-of-freedom haptic interface, are presented to demonstrate the efficacy of the proposed disturbance-observer (DO)-based control approach. This approach circumvents the traditional drawbacks of force sensing while exhibiting the advantages of closed-loop force control in haptic devices. Results show that the proposed disturbance-observer can reliably estimate contact forces at the human-robot interface. The DO-based control approach is experimentally shown to improve haptic interface fidelity over a purely open-loop display while maintaining stable and vibration-free interactions between the human user and virtual environment.

scholarly journals Verification of Finger Joint Stiffness Estimation Method With Soft Robotic Actuator

2020 ◽  
Vol 8 ◽  
Author(s):  
Xiang Qian Shi ◽  
Ho Lam Heung ◽  
Zhi Qiang Tang ◽  
Kai Yu Tong ◽  
Zheng Li
Keyword(s):  
Estimation Method ◽  
Joint Stiffness ◽  
Ground Truth ◽  
Clinical Score ◽  
Metacarpophalangeal Joint ◽  
Finger Joint ◽  
Joint Torque ◽  
Hand Rehabilitation ◽  
Stiffness Characteristic ◽  
Modified Ashworth Scale

Stroke has been the leading cause of disability due to the induced spasticity in the upper extremity. The constant flexion of spastic fingers following stroke has not been well described. Accurate measurements for joint stiffness help clinicians have a better access to the level of impairment after stroke. Previously, we conducted a method for quantifying the passive finger joint stiffness based on the pressure-angle relationship between the spastic fingers and the soft-elastic composite actuator (SECA). However, it lacks a ground-truth to demonstrate the compatibility between the SECA-facilitated stiffness estimation and standard joint stiffness quantification procedure. In this study, we compare the passive metacarpophalangeal (MCP) joint stiffness measured using the SECA with the results from our designed standalone mechatronics device, which measures the passive metacarpophalangeal joint torque and angle during passive finger rotation. Results obtained from the fitting model that concludes the stiffness characteristic are further compared with the results obtained from SECA-Finger model, as well as the clinical score of Modified Ashworth Scale (MAS) for grading spasticity. These findings suggest the possibility of passive MCP joint stiffness quantification using the soft robotic actuator during the performance of different tasks in hand rehabilitation.

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