Sensorless torque/force control

Motion control systems represent a main subsystem for majority of processing systems that can be found in the industrial sector. These systems are concerned with the actuation of all devices in the manufacturing process such as machines, robots, conveyor systems and pick and place mechanisms such that they satisfy certain motion requirements, e.g., the pre specified reference trajectories are followed along with delivering the proper force or torque to the point of interest at which the process occurs. In general, the aim of force/torque control is to impose the desired force on the environment even if the environment has dynamical motion

Multilateral control-based motion copying system for haptic training

This paper proposes a new motion-loading method that utilizes a multilateral control-based scheme for the motion-copying system. The motion-copying system refers to human operator's motion, tracks and preserves it only for being able to reproduce the same result of the motion. Conventionally, only slave system was used for motion-loading phase. The method proposed in this paper offers a way to enable more than one slave side actuator at the phase. With the proposed system, the operator at loading phase can grab the master system which the manipulator was holding at the saving phase. The performance analyses of proposed system are made with the bode plots, and the experiments are held with two degrees-of-freedom actuators. The newly proposed haptic informational reproduction technique can be applied in many areas, especially as the training purposes

Investigation On Force Scaling For Multi Degree Of Freedom Bilateral Teleoperation Control System

A bilateral control system consists of two actuation systems which are separate but sends and receives information to and from each other. Information shared consists of calculated force and position readings from sensors which feed into the control system. When the actuation systems are in the form of robot manipulators, there are at least two degrees of freedom with each degree of freedom has its own force and position values. When these two systems operate simultaneously, a change in force and position for one system triggers the other to coordinate and attempt to maintain the same values of force and position at both sides and this is termed as a master-slave system. In most cases, both systems are identical and the amount of force and position desired is similar. In some real-life applications, the desired amount of force/position is scaled; i.e. smaller or larger force is desired at one end of the system (master/slave). For this purpose, this research proposes a method to scale the force at either master or slave side by using elements of the mass/inertia matrix of the robot manipulator. Four different scaling values were demonstrated in the experiments to show the validity of the proposed method. Results indicate that the method is viable as the forces were scaled correctly as desired

Scaling Of MDOF Micro-Macro Bilateral Control Teleoperation System Using Standardized Modal Space

In future, robots and mechatronic system are required to support human, they should have a lot of abilities such as recognition of the real world based on the complicated human action to environment based on human sensation and so on. The word “Haptic” means sense of touch and haptic information is studied as the third type of multimedia information. Unlike audio and visual information which is transmitted to one direction (unilateral), haptic information is bidirectional information (bilateral), which applied “law of action and reaction” a tactile information in bilateral information. Thus, a bilateral control system with master and slave manipulator to transmit the information bilaterally has been researched. In this thesis, bilateral teleoperation control system is implemented in single link planar and two link planar manipulator which consisted of master and slave system. The modelling of bilateral teleoperation control system is designed with the integration of Disturbance Observer (DOB), Reaction Force/Torque Observer (RFOB)/(RTOB), position controller and force controller. Then further research on micro-macro bilateral teleoperation control system is done on multi degree-of-freedoms (MDOF) which is two link planar manipulator. The micro-macro bilateral control teleoperation system provides the human operator with a sense of feel to a micro or macro environment as if it is in the same scale environment. However, the micro-macro bilateral control system of this thesis consists of same size structure between master and slave manipulator. Thus a standardized modal space method is proposed to achieve for MDOF micro-macro bilateral control teleoperation system. This method able to scale the force and position information between master slave system. It is a novel method for transmission of force and motion in macro environment in order to realize the physical support for the macro activities. Nevertheless, this proposed method able to scale the haptic information between the master and slave system accordingly. To validate the performance of common mode and differential mode of the proposed method, 4 cases of free and contact motion experiments with different nominal mass ratio between master and slave system are conducted. Then the root-mean-square deviation of the nominal mass ratio and scaling α gain from 4 different cases is 1.12×10−5 and 2.55×10−5 fo

Neural network enhanced robot tool identification and calibration for bilateral teleoperation

© 2013 IEEE. In teleoperated surgery, the transmission of force feedback from the remote environment to the surgeon at the local site requires the availability of reliable force information in the system. In general, a force sensor is mounted between the slave end-effector and the tool for measuring the interaction forces generated at the remote sites. Such as the acquired force value includes not only the interaction force but also the tool gravity. This paper presents a neural network (NN) enhanced robot tool identification and calibration for bilateral teleoperation. The goal of this experimental study is to implement and validate two different techniques for tool gravity identification using Curve Fitting (CF) and Artificial Neural Networks (ANNs), separately. After tool identification, calibration of multi-axis force sensor based on Singular Value Decomposition (SVD) approach is introduced for alignment of the forces acquired from the force sensor and acquired from the robot. Finally, a bilateral teleoperation experiment is demonstrated using a serial robot (LWR4+, KUKA, Germany) and a haptic manipulator (SIGMA 7, Force Dimension, Switzerland). Results demonstrated that the calibration of the force sensor after identifying tool gravity component by using ANN shows promising performance than using CF. Additionally, the transparency of the system was demonstrated using the force and position tracking between the master and slave manipulators

Hydraulisen puomin voimatakaisinkytketty etäohjaus

Teleoperation has been under study from the mid 1940s, when the first mechanical master-slave manipulators were built to allow safe handling of nuclear material within a hot cell. Since then, need to operate within dangerous, out of reach, uncomfortable, or hazardous environments has then motivated researchers to study teleoperation further. In this thesis, teleoperation of a hydraulic manipulator with electrically driven master manipulator was studied. The workspace of the hydraulic slave manipulator is 5 m in height and it can reach 3 m. The master manipulator has a workspace approximating full arm movement pivoting at the shoulder. Further, the slave manipulator is capable of lifting over 1000 kg, while the master manipulator can lift only 2 kg. Objective of this thesis is to implement virtual decomposition control (VDC) type controller to the master manipulator and create communication channel for the two manipulators. The VDC approach is a subsystem model based feedforward controller. Similar controller for the slave manipulator has been implemented previously. Performance of the developed teleoperation system will be evaluated with experimental implementation measuring the free space motion tracking in two degrees of freedom motion. Results from the experimental implementation indicate accurate motion tracking between the two manipulators. Experimental results indicate less than 15 mm position error between the two manipulators, which considering the size of the HIAB can be considered promising

Design, Development and Force Control of a Tendon-driven Steerable Catheter with a Learning-based Approach

In this research, a learning-based force control schema for tendon-driven steerable catheters with the application in robot-assisted tissue ablation procedures was proposed and validated. To this end, initially a displacement-based model for estimating the contact force between the catheter and tissue was developed. Afterward, a tendon-driven catheter was designed and developed. Next, a software-hardware-integrated robotic system for controlling and monitoring the pose of the catheter was designed and developed. Also, a force control schema was developed based on the developed contact force model as a priori knowledge. Furthermore, the position control of the tip of the catheter was performed using a learning-based inverse kinematic approach. By combining the position control and the contact model, the force control schema was developed and validated. Validation studies were performed on phantom tissue as well as excised porcine tissue. Results of the validation studies showed that the proposed displacement-based model was 91.5% accurate in contact force prediction. Also, the system was capable of following a set of desired trajectories with an average root-mean-square error of less than 5%. Further validation studies revealed that the system could fairly generate desired static and dynamic force profiles on the phantom tissue. In summary, the proposed force control system did not necessitate the utilization of force sensors and could fairly contribute in automatizing the ablation task for robotic tissue ablation procedures