Compliance Control Algorithm Research Articles

Development of a Multi-Robot System for Pier Construction

The construction industry is a challenging field for the application of robots. In particular, bridge construction, which involves many tasks at great heights, makes it difficult to implement robots. To construct a bridge, it is necessary to build numerous piers that can support the bridge deck. Pier construction involves a series of tasks including rebar connection, formwork installation, concrete pouring, formwork dismantling, and formwork reinstallation. These activities require working at heights, presenting a significant risk of falls. If bridge construction could be performed remotely using robots instead of relying on human labor, it would greatly contribute to the safety of bridge construction. This paper proposes a multi-robot system capable of remote operation and automation for rebar structure connection, concrete pouring, and concrete vibrating tasks in pier construction. The proposed multi-robot system for pier construction is composed of three robot systems. Each robot system consists of a robot arm mounted on a mobile robot that can move along rails. And to apply the proposed system to a construction site, it is essential to implement a compliance control algorithm that adapts to external forces. In this paper, we propose an admittance control that takes into account the weight of the tool for the compliance control of the proposed robot, which performs tasks by switching between various construction tools of different weights. Furthermore, we propose a synchronization control method for the multi-robot system to connect reinforcing structures. We validated the proposed algorithm through simulation. Furthermore, we developed a prototype of the proposed system to verify the feasibility of the suggested hardware design and control.

Research on a Biomimetic Flexible Ball Joint With Variable Stiffness for Robots

Abstract The human ball joint is a compact and flexible 3-degree-of-freedom (DOF) composite joint. The ball joints commonly used in robot design lack active driving capability. Ball joints with active drive generally consist of three single-degree-of-freedom joints connected in series, which is a noncompacted structure and easily leads to singular postures. In order to meet the demand for high-performance composite joint modules for service robots, this article designs a flexible biomimetic spherical robot joint with variable stiffness characteristics: the mechanism of muscle parallel antagonistic drive and ligament wrapping constraint is simulated; three parallel branch chains are used to drive three composite degrees-of-freedom; ropes, soft airbags, and series elastic drive gears are used to form a flexible transmission system; the contour of the rope winch has been optimized with the aim of transmission stability; and a pneumatic variable stiffness soft structure has been designed and fabricated. A compliance control algorithm for joints was developed based on the principle of impedance control. The research results indicate that the biomimetic ball-and-socket joint has a compact structure, a wide range of motion and good motion tracking performance, variable stiffness performance, and flexible interaction ability.

An Active Landing Recovery Method for Quadrotor UAV: Localization, Tracking and Buffering Landing

This paper proposes a principle of fully autonomous ground mobile landing recovery of Unmanned Aerial Vehicles (UAV) for the problems of relatively fixed landing point, passive recovery, poor flexibility, and environmental adaptability, which mainly includes localization, landing point tracking, and buffering landing for quadrotor UAV. Firstly, aiming at the problem that it is difficult to accurately obtain the position of a UAV in dynamic mobile landing recovery, a target location method based on Asynchronous Multisensor Information Fusion(AMIF) and servo turntable focus tracking is proposed. Secondly, to achieve fast and high-precision tracking of UAVs, a tracking control strategy of an independently driven landing recovery system and a Stewart six-degree of freedom platform is proposed. Then, to solve the problems of large impact force and center of gravity instability in the landing process of UAV, a stationarity control algorithm based on model prediction and a compliance control algorithm based on adaptive variable impedance are designed to achieve active compliance control while adjusting the position and attitude of the receiving surface in real-time. Finally, a quadrotor unmanned landing and recovery experimental platform is built to verify the feasibility of the ground mobile landing and recovery strategy proposed in this paper and the effectiveness of the control algorithm.

Easy-to-Deploy Combined Nasal/Throat Swab Robot With Sampling Dexterity and Resistance to External Interference

Robots have been used extensively in the battle against the COVID-19 pandemic since its outbreak. One prominent direction is the use of robots for swab sampling, which not only solves the shortage of medical staffs, but also prevents them from being infected during face-to-face sampling. However, a massive deployment of sampling robots is still not achievable due to their high costs, safety concerns, deployment complexity, and so on. In this letter, we propose a flexible, safe, and easy-to-deploy swab robot in a compact bench-top system. The robot can perform nasal/throat swab sampling tasks as dexterous as a human manual operation. The bio-mimetic rigid interior and soft exterior design guarantee the sampling robot with both flexibility and safety. Furthermore, the integration of 3-D fiber Bragg grating (FBG) based shape sensor and multi-axis force sensor may enhance the control performance. A dedicated constrained compliance control (CCC) algorithm was developed to tackle the unexpected interactions during sampling, which ensures the validity and safety of the sampling under disturbance. Various experiments are conducted to validate our system and prove its feasibility, flexibility, high safety, and efficiency for both nasal/throat swab sampling tasks. The proposed system is promising to be massive duplicated for robotic swab sampling.

Research and Ground Verification of the Force Compliance Control Method for Space Station Manipulator

The space station manipulator does lots of tasks with contact force/torque on orbit. To ensure the safety of the space station and the manipulator, the contact force/torque of manipulator must be controlled. Based on analyzing typical tasks’ working flows and force control requirements, such as ORU (orbit replacement unit) changeout and dual arm collaborative payload transport, an impedance control method based on wrist 6 axis force/torque feedback is designed. For engineering implementation of the impedance control algorithm, the discretization method and impedance control parameters selection principle are also studied. To verify the compliance control algorithm, a ground experiment platform adopting industrial manipulators is developed. In order to eliminate the influence of gravity, a real-time gravity compensation algorithm is proposed. Then, the correctness of real-time gravity compensation and force compliance control algorithm is verified on the experiment platform. Finally, the ORU replacement and dual arm collaborative payload transport experiments are done. Experimental results show that the force compliance control method proposed in this paper can control the contact force and torque at the end of the manipulator when executing typical tasks.

Parameter identification and adaptive compliant control of rehabilitation exoskeleton based on multiple sensors

• We establish a coupling kinematics/dynamics model by human-machine coupling relationship. • We address an estimation method of active joint torque of human lower limbs. • A reference trajectory adaptive compliance control algorithm is proposed. To help rehabilitation of patients with lower limb dysfunction, a sitting/lying exoskeleton robot is designed for lower limb rehabilitation. Firstly, a coupling kinematics/dynamics model, including the wearer and exoskeleton, is established by the in-depth analysis of human-machine coupling relationship, and the prototype structure is introduced. Furthermore, according to the kinetic parameter identification method, an estimation method of active joint torque of human lower limbs is proposed to realize the prediction of human motion intention, which is the basis of the reference motion trajectory. Moreover, a reference trajectory adaptive compliance control algorithm is proposed. Finally, the human-computer interaction force is measured by the torque sensor, the effectiveness of the parameter identification and compliance control algorithm is verified.

Compliance Control of Slave Manipulator Using EMG Signal for Telemanipulation

Telemanipulation systems have been widely utilized in industrial, surgical, educational, and even military fields. One of the important issues is that when a robot interacts with environment or objects, it can damage the robot itself or the objects due to hard contact. To address this problem, we propose a novel compliance control of a slave robot using the electromyography (EMG) signal, which is measured by the sensors attached onto the master operator’s arm. The EMG signal is used since it is easy to process and it provides humans with an intuitive capability to perform the operational work. Furthermore, it has been proved that the EMG signal is useful in the control of the stiffness of the slave robot. This research identifies the muscle that is the best suitable to a precision-grip operation, and a series of experiments were performed. A compliance control algorithm with a variable stiffness of a slave robot is proposed, where the stiffness is changed based on the EMG signal, and it is confirmed by a series of experiments using a two-channel force/position teleoperation architecture.

Compliance Control Using Hydraulic Heavy-Duty Manipulator

Active compliance control is one of the necessary prerequisites for the fine manipulation of hydraulic heavy duty manipulators (HHDMs). The establishment of a rigid–flexible coupling machine–hydraulic multibody dynamics model and an active compliance control algorithm for HHDM are the key problems to be solved urgently in the compliance control of heavy duty manipulators. In this paper, a multibody dynamics model of a machine–hydraulic system with seven degrees of freedom is developed with consideration of HHDM characteristics, such as multi-input multioutput, nonlinearity, and rigid-flexible coupling. Meanwhile, a position/force same loop control algorithm for the compliance control of HHDM is proposed based on genetic neural network. Specifically, the force control system is decomposed into subsystems, while the feedback position and force are output through the processing of the joint position controller, torque controller, and multibody dynamics model. Cosimulation results present the feasibility and effectiveness of the proposed dynamics model and control algorithm. Moreover, the experimental environment and the HHDM control system are also developed, while the operation experiment of the control system for HHDM is accordingly conducted. Experiment results show that the control system can realize precise control of position and force, and can successfully complete the function of active compliance control operation.

케이블 구동 메커니즘을 이용한 재활 로봇의 능동 컴플라이언스 제어

In this paper, we proposed a TDC based FIT sensorless active compliance control algorithm for a rehabilitation robot (KARES Ⅱ). The preference of compliance of the disabled is presented by clinical testing at Korea National Rehabilitation Center with the disabled. The KARES Ⅱ was designed to work 12 pre-defined tasks which are very essential for helping the disabled. Among the tasks, some contact tasks between the robot and the disabled exist. Therefore, IDC based F/T sensorless compliance control algorithm is developed for these tasks without additional cost. We verified the proposed algorithm with experiment. Also for the practical use, suitable compliance for contact tasks is chosen by clinical testing at Korea National Rehabilitation Center.<br/>

Control of a Robot Based on Fusion of Visual and Force/Torque Sensor Information. Manipulation of a Deformable Object.

Since there exist a lot of deformable objects in our daily life, method of manipulation of a deformable object for a robot is expected not only in industrial manufacturing but also in life support. Generally, a force/torque sensor is used in playing a contact task for a rigid object by a robot. However, only a force/torque sensor is not enough in handling of a deformable object by a robot. In this paper, a fusion algorithm by integrating data from both a force/torque sensor and a visual sensor is proposed for a robot to play a contact task in which an aluminum peg fixed on the robot hand is inserted into a hole installed on a deformable plate. To complete the task, a high-speed camera is used and a real time processing algorithm is developed to detect deformation of the central line of the hole. Then, the results of visual processing are integrated with data of the force/torque sensor using the proposed compliance control algorithm for a robot in playing the task. The effectiveness of the proposed method has been demonstrated through experiments.

3914 視覚と力覚のセンサフュージョンによるロボットの制御 : 変形物体の操作

Ability of handling of a deformable object for a robot is expected not only in industrial manufacturing but also in human life support. A force/torque sensor is frequently used for robot control in playing a contact task with a rigid object. However, it is not enough for controlling a robot in handling of a deformable object. In this paper, a sensor fusion algorithm is proposed to control a robot to insert an aluminum peg set up on the robot hand into a deformable hole. To completing the task, a high-speed camera is used and a real time processing algorithm is developed to detect the deformation of the central line of the hole. The results of real time visual processing are integrated with information of a force/torque sensor for controlling a robot in playing the task using a proposed compliance control algorithm. The effectiveness of proposed method has been demonstrated through experiments.

A neural network-based classification of environment dynamics models for compliant control of manipulation robots

In this paper, a new method for selecting the appropriate compliance control parameters for robot machining tasks based on connectionist classification of unknown dynamic environments, is proposed. The method classifies the type of environment by using multilayer perceptron, and then, determines the control parameters for compliance control using the estimated characteristics. An important feature is that the process of pattern association can work in an on-line mode as a part of selected compliance control algorithm. Convergence process is improved by using evolutionary approach (genetic algorithms) in order to choose the optimal topology of the proposed multilayer perceptron. Compliant motion simulation experiments with robotic arm placed in contact with dynamic environment, described by the stiffness model and by the general impedance model, have been performed in order to verify the proposed approach.

An actively compliable probing system

A new probing mechanism and an associated active compliance control algorithm have been developed for in-circuit test of a PCB (printed circuit board). Commercially available robotic probing devices are incapable of controlling contact force generated when a rigid probe contacts with a solder joint at high speed. This uncontrollable excessive contact force often makes some defects on the surface of the solder joint, which is plastically deformable over some limited contact force. This force also makes unstable contact motions resulting in unreliable test data. To overcome these problems, we propose a serially connected macro and micro manipulator equipped with active compliance capability for safe and reliable in-circuit test. Moreover, with this probe the depth of penetration onto a solder joint can be regulated after contact. This article describes the design characteristics, modeling, and control scheme of the newly proposed devices. The comparison of conventional passive compliance and force feedback control methods with the proposed control scheme for the contact force control is presented. The results obtained from a series of experiments clearly show the effectiveness of the proposed system.