Slave Arm Research Articles

Development of a full ocean depth hydraulic manipulator with heavy-duty capacity

The underwater manipulator is a versatile tool commonly used for various underwater operations. In this study, we developed a heavy-duty hydraulic manipulator capable of operating at full ocean depth. The overall system design integrates both the mechanical structure and the electric control system. The master arm controls the slave arm by transmitting control signals to the controller and valve box. The structural design of the elbow and wrist joints has been optimized to enhance the manipulator's underwater performance and operational range. Laboratory tests demonstrated the manipulator’s excellent response consistency and tracking capability across a wide range of motion. During sea trials in the Mariana Trench, the manned submersible Fendouzhe successfully deployed the manipulator, showcasing its exceptional ability to complete complex tasks.

Remote tele‐operation using model reference discrete‐time sliding mode control

AbstractIn this article, a dissipativity based discrete time sliding mode controller is proposed for bilateral tele‐operation in presence of communication delays and packet losses. The controllers for both master and slave arm are designed to follow a predefined impedance dynamics with dissipative characteristics. The slave arm controller is designed as a two layered structure. The first layer uses the tracking error between master and slave to create a target velocity profile based on the user defined impedance dynamics. The second layer uses this target velocity profile, slave motion and the contact forces to design a reaching law based discrete time sliding mode controller. A model following reaching law approach is used to design the sliding mode control which alleviates the chattering in the input by removing the impact of the accumulated effects of the past disturbance from the system. Moreover, an adaptive tuning method is used for the switching gain of the sliding mode control so that the controller can be designed even when exact information on the uncertainty bounds are unknown. Numerical simulations are presented for Phantom Omni arm to show the efficacy of the proposed method.

Design and Implementation of Force Sensation and Feedback Systems for Telepresence Robotic Arm

Humans put their own lives aside to save other human’s life and perform risky and dangerous activities. The risk can be reduced by using new technologies. This research study focuses on telepresence and teleoperation systems with motion and force control systems that replace humans in hazardous workspaces. In telepresence, the system helps humans to visualize the environment in real-time. In teleoperation, the system provides sensation to assist human beings in performing out-of-reach and dangerous operations safely as in real, providing a shadow hand to the operator. In this study, a system is developed that consists of a slave robotic arm and a master wearable device with bidirectional communication between the robotic arm and operator (master wearable device). It also presents a gesture-controlled robotic arm that uses sensors to read and translate human arm movements as commands. The slave robotic arm, senses applied force on an object and a master wearable device develops the force according to sensed force, in a result operator senses/feels the same object in the control room at distance. The slave robotic arm also mimics the operator arm to reach the proper position of an object. Several experiments were conducted with untrained personnel and satisfactory results were yielded, which showed that the motion and force replication is 90-95% accurate.

An algorithm for trajectory optimization of dual-arm coordination based on arm angle constraints

In this paper, the motion planning of a dual-arm robot with kinematic constraints is studied based on arm-angle constraints. When a dual-arm robot moves a common object, a closed kinematic chain is formed between the dual-arm and the object. The standard sampling-based trajectory planning algorithm solves the problem with closed-chain constraint, but this causes other problems; the running time increases, the success rate decreases, and the motion trajectory of the end effector is not smooth resulting in large output error. Therefore, this paper proposes a dual-arm coordinated trajectory optimization algorithm based on arm-angle constraints. Firstly, the kinematics of the dual-arm robot is modeled and analyzed, and the definition of the arm-angle in a seven-axis robot is proposed, the workspace of the dual-arm coordinated operation is considered to constrain it, the kinematics equation combined with the single/multi-objective optimization algorithm is used to optimize the end output error, and the joint trajectory is parameterized. This paper solves the problems that the slave arm lags behind the main arm, the motion trajectory of the dual-arm is not smooth, and the dual-arm are squeezed due to internal force during the coordinated movement of the dual-arm. The trajectory optimization improves the synchronization of the coordinated operation of the dual-arm, reduces the output error of the velocity and acceleration at the end of the dual-arm. After limiting the arm-angle, dual-arm manipulation is anthropomorphic the robot does not produce distorted arm configurations.

Obstacle Avoidance Path Planning for the Dual-Arm Robot Based on an Improved RRT Algorithm

In the future of automated production processes, the manipulator must be more efficient to complete certain tasks. Compared to single-arm robots, dual-arm robots have a larger workspace and stronger load capacity. Coordinated motion planning of multi-arm robots is a problem that must be solved in the process of robot development. This paper proposes an obstacle avoidance path planning method for the dual-arm robot based on the goal probability bias and cost function in a rapidly-exploring random tree algorithm (GA_RRT). The random tree grows to the goal point with a certain probability. At the same time, the cost function is calculated when the random state is generated. The point with the lowest cost is selected as the child node. This reduces the randomness and blindness of the RRT algorithm in the expansion process. The detection algorithm of the bounding sphere is used in the process of collision detection of two arms. The main arm conducts obstacle avoidance path planning for static obstacles. The slave arm not only considers static obstacles, but also takes on the role of the main arm at each moment as a dynamic obstacle for path planning. Finally, MATLAB is used for algorithm simulation, which proves the effectiveness of the algorithm for obstacle avoidance path planning problems for the dual-arm robot.

A dual-arm manipulation strategy using position/force errors and Kalman filter

This paper presents a new coordination manipulation strategy for a custom-made dual-arm robot. With master and slave coordination infrastructure, both spatial relation and sense of touch are considered to hold an object stably. Given the known trajectory of the master arm, the slave arm fuses position and force commands by using the Kalman filter to yield optimal compensation amounts. The proposed strategy has been experimentally evaluated, and the results confirm that it was capable of dealing with fragile and flexible objects. In addition, the influence of the loop time of the digital controller on force control for this task was also investigated in mathematical and simulated ways. Furthermore, a series of experiments were designed to explore the effects that have influences on errors in force control. The main factors that affect force control error were analyzed.

Coordinated compliance control of dual-arm robot astronaut for payload operation

Dual-arm robot astronaut has more general and dexterous operation ability than single-arm robot, and it can interact with astronaut more friendly. The robot will inevitably use both arms to grasp payloads and transfer them. The force control of the arms in closed chains is an important problem. In this article, the coordinated kinematic and dynamic equations of the dual-arm astronaut are established by considering the closed-chain constraint relationship. Two compliance control methods for dual-arm astronaut coordinated payload manipulating are proposed. The first method is called master–slave force control and the second is the shared force control. For the former, the desired path and operational force of the master arm should be given in advance and that of slave arm are calculated from the dual-arm robot closed-chain constraint equation. In the share control mode, the desired path and end operational force of dual arms are decomposed from the dual-arm robot closed-chain constraint equation directly and equally. Finally, the two control algorithms are verified by simulation. The results of analysis of variance of the simulation data show that the two control methods have no obvious difference in the accuracy of force control but the second control method has a higher position control accuracy, and this proves that the master–slave mode is better for tasks with explicit force distribution requirements and the shared force control is especially suitable for a high-precision requirement.

Trance-it to the Future

Trance-it to the Future

Human-Inspired Control of Dual-Arm Exoskeleton Robots With Force and Impedance Adaptation

Humans can adapt to complex environments by voluntarily adjusting the impedance parameters and interaction force. Traditional robots perform tasks independently without considering their interactions with the external environment, which leads to poor flexibility and adaptability. Comparatively, humans can adapt to complex environments by voluntarily adjusting the impedance parameters and interaction force. In order to solve the problems of human–robot security and adaptability to unknown environment, a human-inspired control with force and impedance adaptation is proposed to interact with unknown environments and exhibit this biological behavior on the developed dual-arm exoskeleton robots. First, we propose a computationally model utilizing the sampled surface electromyogram (sEMG) signals to calculate the human arm endpoint stiffness and define a co-contraction index to describe the dynamic behaviors of the muscular activities in the tasks. Then, the obtained human limb impedance stiffness parameters and the sampling position information are transferred to the slave arm of the exoskeleton as the input variables of the controller in real-time. In addition, a variable stiffness observer is used here to compensate for the errors of the calculated stiffness by sEMG signals. The experimental studies of human impedance transfer control have been conducted to show the effectiveness of the developed approach. Results of the experimental suggest that the proposed controller can achieve human motor adaptation and enable the subjects to execute a skill transfer control by a dual-arm exoskeleton robot.

Vision-based hand-eye calibration for robot-assisted minimally invasive surgery.

The knowledge of laparoscope vision can greatly improve the surgical operation room (OR) efficiency. For the vision-based computer-assisted surgery, the hand-eye calibration establishes the coordinate relationship between laparoscope and robot slave arm. While significant advances have been made for hand-eye calibration in recent years, efficient algorithm for minimally invasive surgical robot is still a major challenge. Removing the external calibration object in abdominal environment to estimate the hand-eye transformation is still a critical problem. We propose a novel hand-eye calibration algorithm to tackle the problem which relies purely on surgical instrument already in the operating scenario for robot-assisted minimally invasive surgery (RMIS). Our model is formed by the geometry information of the surgical instrument and the remote center-of-motion (RCM) constraint. We also enhance the algorithm with stereo laparoscope model. Promising validation of synthetic simulation and experimental surgical robot system have been conducted to evaluate the proposed method. We report results that the proposed method can exhibit the hand-eye calibration without calibration object. Vision-based hand-eye calibration is developed. We demonstrate the feasibility to perform hand-eye calibration by taking advantage of the components of surgical robot system, leading to the efficiency of surgical OR.

The Implementation of Bilateral Control Symmetrical Position, Force Reflection and Feedback Force on the Haptic Manipulator

Humans often encounter obstacles in doing their work. Especially if the work is related to an emergency situation that concerns the safety of human life, it needs quick and appropriate handling. Telerobotic technology that has a haptic function is one solution to these problems. In this study a system of 1 DOF haptic manipulator with slave master configuration was developed using bilateral haptic manipulator control. In bilateral control the position and information are transmitted in two directions between two manipulators. Position information is obtained using a potentiometer and force information is obtained by representing the force with the current using the WCS2702 sensor. There are three control methods used, namely bilateral symmetrical position control, bilateral reflection force control and force feedback bilateral control. The best method of control is the bilateral feedback force control. In the force feedback bilateral control system, the slave can move following the master movement with a ± 2° position error. When the slave arm is held by a hard object, the master arm is also restrained with ± 11° position error. Whereas when the slave arm is held by a soft object, the reflection of the object is felt by the master arm with ± 10 position error. Movement of the master and slave arms is lighter than using bilateral control of symmetrical position.

Hybrid force/position control of master and slave robotic systems

ABSTRACT For certain robotic applications, the manipulator should be tele-operated to reach a specified position or track a desired trajectory, with desired compliance, in a hazardous working environment. Hence, how to construct a two-way position/force-transmitted master/slave system for tele-manipulating end-effector motion by an operator is a relevant research topic. Here, a novel low-cost system structure has been constructed with a Novint Falcon tactile device as the master control and a 5 DOF robot arm the slave end. Appropriate position and contact force transformation between both mechanisms were established and transmitted through an RS232 interface. An operator can manipulate the Novint Falcon tactile device to deliver the position and force output commands to the slave robot arm controller for monitoring the position and force responses of the end-effector. A torque/force sensor was installed at the robotic wrist to measure the contact force, and feedback to the master end as hand feeling for two-way impedance motion harmonization. The experimental results show that the operator can tele-operate the robotic manipulator to follow the commanded trajectory with appropriate contact force and get proportional force feedback to the operator’s hand, via the Novint Falcon device.

Peg-in-hole assembly based on master-slave coordination for a compliant dual-arm robot

PurposeThe paper aims to propose an assembly scheme based on master–slave coordination for a compliant dual-arm robot to complete a peg-in-hole assembly task.Design/methodology/approachThe proposed assembly scheme is inspired by the coordinated behaviors of human beings in the assembly process. The left arm and right arm of the robot are controlled to move alternately. The fixed arm and the moving arm are distinguished as the slave arm and the master arm, respectively. The position control model is used at the uncontacted stage, and the torque control model is used at the contacted stage.FindingsThe proposed assembly scheme is evaluated through peg-in-hole assembly experiments with different shapes of assembly piece. The round, triangle and square assembly piece with 0.5 mm maximum clearance between the peg and the hole can be assembled successfully based on the proposed method. Furthermore, three assembly strategies are investigated and compared in the peg-in-hole assembly experiments with different shapes of assembly piece.Originality/valueThe contribution of this study is that the authors propose an assembly scheme for a compliant dual-arm robot to overcome the low positioning accuracy and complete the peg-in-hole assembly tasks with different shapes parts.

A Subject-Specific Four-Degree-of-Freedom Foot Interface to Control a Surgical Robot

This article introduces a passive four-degree-of-freedom foot interface to control a robotic surgical instrument. This interface is based on a parallel–serial hybrid mechanism with springs and force sensors. In contrast to existing switch-based interfaces that can command a slave robot arm at constant speed in only discrete directions, the novel interface provides an operator with intuitive control in continuous directions and speed with force and position feedback. The output command of the interface was initially derived based on the kinematics and statics of the interface. Since distinct movement patterns among different subjects were observed in a pilot test, a data-driven approach using independent component analysis was developed to convert the foot inputs to the control commands of the user. The capability of this interface in controlling a robotic arm in multiple degrees of freedom was further verified with a teleoperation test.

Coordination Control of a Dual-Arm Exoskeleton Robot Using Human Impedance Transfer Skills

This paper has developed a coordination control method for a dual-arm exoskeleton robot based on human impedance transfer skills, where the left (master) robot arm extracts the human limb impedance stiffness and position profiles, and then transfers the information to the right (slave) arm of the exoskeleton. A computationally efficient model of the arm endpoint stiffness behavior is developed and a co-contraction index is defined using muscular activities of a dominant antagonistic muscle pair. A reference command consisting of the stiffness and position profiles of the operator is computed and realized by one robot in real-time. Considering the dynamics uncertainties of the robotic exoskeleton, an adaptive-robust impedance controller in task space is proposed to drive the slave arm tracking the desired trajectories with convergent errors. To verify the robustness of the developed approach, a study of combining adaptive control and human impedance transfer control under the presence of unknown interactive forces is conducted. The experimental results of this paper suggest that the proposed control method enables the subjects to execute a coordination control task on a dual-arm exoskeleton robot by transferring the stiffness from the human arm to the slave robot arm, which turns out to be effective.

Архитектура тренажерной системы подготовки операторов радиационно стойких манипуляторов

Nowadays Industrial robots of different kinematic structures and functionality are widely used nowadays in different areas of industry and most of them function autonomously with preprogrammed set of actions or typical trajectories. Some special purposes mobile and stationary robots are human-controlled and in most cases require qualified operator skills. For example, in nuclear industry the mechanical and electro-mechanical “master arm – slave arm” manipulators are widely used. Modern approaches of control systems and human machine interfaces designs allow to eliminate direct copy of kinematic configuration of manipulator arms, add semi-automatic and automated control modes. Key feature of such manipulator systems is a presence of human in control loop, by reason of variety and complexity of manipulations and, in some cases, non-deterministic environment. Due to these factors, it is very desirable to form operator sustainable skills to control such manipulators, including learning process using training systems. This article describes general approaches and practical aspects of the operator training and qualification system for arm-based special purpose manipulators. The set of training system functions include: general manipulator control (basic motion) and grasping actions, manipulator operations in restricted working areas, operator actions using virtual reality helms and multi-monitor visualization, etc. The hardware and software architecture of training system should allow effective training process and teamwork of trainee and instructor to reach good results. The paper proposes ROS-based software part of training system with description of inter-process communication messages, data formats, integration with database and following analysis of trainee action.

Control of Bilateral Teleoperation System Consisting of Heterogeneous Manipulators with Communication Delay

This paper proposes a new control method for bilateral teleoperation systems with communication delay. Under the proposed control law, the passivity from external forces to velocities and the position synchronization in the working spaces are attained. The master and slave arms can have different mechanical structures and have redundant degree-of-freedom. The proposed control can work even on singular postures, because it uses no inverses of Jacobian matrices. The bad effect of the transmission delay on stability is canceled by local damping terms, since there exists a dissipativity for a supply rate on the actions of the position-signal’s delay and the local damping term. We show the property of the storage functional for the supply rate, which makes it possible to show the synchronization via Barbalat’s lemma. When both the arms are stopped, the force from the environment in the working space is properly transmitted to the other arm as the force on the operation space balancing with the human’s manipulation force.

Robot Arm Analysis based on Master Device Pneumatic Actuators

Advances in technology have expanded the use of soft actuators in various fields especially in robotics, rehabilitation and medical field. Soft actuator development provides many advantages, primarily being simple structures, high power to weight ratio, good compliance, high water resistance and low production cost. However, most soft actuators suffer the problem of being oversized which could potentially hurt users as it is often made of hard materials such as steels and hard rigid plastics. Current drawbacks of soft actuator implementation in robotic arms are on its excessive weights, causing these robots to be difficult to set up by patients themselves which in turn makes it less applicable for home rehabilitation training program. Hence, there is a need to design a soft actuator which is safe and more flexible, especially for applications in areas of patients in rehabilitation area or in-house rehabilitation program. In this paper, we propose the design of robot arm using master device pneumatic actuator and analyse the implementation for the above purpose. The system comprises primarily of the master and slave arms, two accelerometers and two potentiometers providing references for attitude control, six quasi-servo valves, and SH-7125 microcontroller. Our proposed design exhibits functions of the actuator that has been generated from elastic deformation of extension and contraction of the cylinder structure when high pneumatic pressure is supplied to the chamber. The control performance of the device is investigated using simulation method, whereby the rational model of the robot arm and the quasi servo valve with the embedded controller is implemented and analysed. It is found that the analysed results of the model approved well with the desired values.

Hardware-in-the-loop simulation of massive-payload manipulation on orbit

This paper describes a hardware-in-the-loop simulation of massive-payload manipulation on orbit using a master–slave teleoperation system. The main problems in teleoperating a space robot arm from the earth to manipulate a massive payload are communication delay, unexpected excessive force generated between the slave arm and the payload, and geometric/dynamic modeling error. In order to overcome those problems, a teleoperation system using mixed force and motion commands is discussed. The teleoperation system is verified by performing hardware-in-the-loop simulations.

Motion mapping of the heterogeneous master–slave system for intuitive telemanipulation

Heterogeneous master–slave robots are widely used as both the assistive robot system for the elder/disabled people and the teleoperation robot system in dangerous environments. For the sake of intuitive teleoperation, motion mapping should be applied to keep the slave arm possessing the similar configuration of the master arm in the whole course of telemanipulation. We propose a motion mapping on the joint analog level based on unit dual quaternions (UDQs) for the telecontrol of a heterogeneous slave robot arm via the motion of human master arm. First, we analogize the links of the slave robot to the links of the human master arm, and accordingly group the slave arm joints into “shoulder,” “elbow,” and “wrist” joint analog sets. Then, we capture the motion of the human master arm via a wearable motion capture system and take it as the motion order of the slave arm. Finally, we solve the motion of slave robot arm’s joint via UDQ-based 1-, 2-, and 3-Degree of freedom (DOF) orientation error UDQ decomposition algorithms that are suit for solving a typical class of robotic slave arms. As a result, the operator can manipulate the heterogeneous robot system intuitively and conveniently, and the fatigue degree and error rate of the user can be significantly reduced, and thus the safety of teleoperation in an unstructured and constrained environment can be significantly improved.