Experimental Research of Force Feedback Dataglove Based on Pneumatic Artificial Muscle

Force feedback dataglove is an important interface of human-machine interaction between manipulator and virtual assembly system, which is in charge of the bidirectional transmission of movement and force information between computer and operator. The exoskeleton force feedback dataglove is designed taking the pneumatic artificial muscle as actuator, meanwhile, its structure and work principle are introduced, and the force control problem is analyzed and researched by experiment. The mathematic model of grasping rigid object for finger is established. Considering the friction of tendon-sheath system and finger deformation, the closed-loop force control for a single joint, a single finger and multi-fingers are studied respectively by the feedforward proportional-integral（PI） control method with variable arguments. On the premise of the force smoothness, the control error of the force exerted on the finger joint is in the range of ±0.25 N, which meets the requirement of force feedback. By experimental analysis, the reason of force fluctuation is that the finger joint has a small amplitude quiver, and the consistent change tendency of the force between proximal interphalangeal（PIP） joint and distal interphalangeal（DIP） joint results from their angle coupling relationship.

Force Feedback Coupling with Dynamics for Physical Simulation of Product Assembly and Operation Performance

Most existing force feedback methods are still difficult to meet the requirements of real-time force calculation in virtual assembly and operation with complex objects. In addition, there is often an assumption that the controlled objects are completely flee and the target object is only completely fixed or flee, thus, the dynamics of the kinematic chain where the controlled objects are located are neglected during the physical simulation of the product manipulation with force feedback interaction. This paper proposes a physical simulation method of product assembly and operation manipulation based on statistically learned contact force prediction model and the coupling of force feedback and dynamics. In the proposed method, based on hidden Markov model （HMM） and local weighting learning （LWL）, contact force prediction model is constructed, which can estimate the contact force in real time during interaction. Based on computational load balance model, the computing resources are dynamically assigned and the dynamics integral step is optimized. In addition, smoothing process is performed to the force feedback on the synchronization points. Consequently, we can solve the coupling and synchronization problems of high-frequency feedback force servo. low-frequency dynamics solver servo and scene rendering servo, and realize highly stable and accurate force feedback in the physical simulation of product assembly and operation manipulation. This research proposes a physical simulation method of product assembly and operation manipulation.

FORCE FEEDBACK DATAGLOVE BASED ON PNEUMATIC ARTIFICIAL MUSCLES

An exoskeleton force feedback dataglove is developed, which uses the pneumatic artificial muscles as actuators. On the basis of the simplified hand model, the motion equation is deduced according to the theory of Denavit-Hartenberg. The model of the equivalent contact forces exerted by the object on the finger is proposed. By the principle of virtual work, the static equilibrium of finger is established. The force Jacobian matrix of finger is calculated, and then the joint torques of the finger when grasping objects are obtained. The theory and structure of the force feedback datagolve are introduced. Based on the theory of motion stabilization of four-bar linkage, the flexion angles of joints are measured. The torques on finger joints caused by the output forces of pneumatic artificial muscles are calculated. The output forces of pneumatic artificial muscle, whose values are controlled by its inner pressure, can be calculated by the joint torques of the finger when grasping objects. The arms of force, driving torques and the needed output forces of pneumatic muscle are calculated for each joint of the index finger. The criterion of output force of pneumatic muscle is given.

PI force feedback control for large flexible structure vibration with active tendons

Active tendon, consisting of a displacement actuator and a collocated force sensor, was first presented by Preumont and his co-workers to attenuate the vibration of large flexible space structures, and the control algorithm adopted by them was integral force feedback. This paper presents a new proportional-integral （PI） force feedback algorithm to achieve larger damping ratios for the structure without the requirement of structure model. Stability of the control system is shown, and simulations of a structure similar to JPL-MPI demonstrate the effectiveness of the proposed algorithm for vibration control of space structures.

Orthodontic simulation system with force feedback for training complete bracket placement procedures

Background A virtual system that simulates the complete process of orthodontic bracket placement can be used for pre-clinical skill training to help students gain confidence by performing the required tasks on a virtual patient.Methods The hardware for the virtual simulation system is built using two force feedback devices to support bi-manual force feedback operation.A 3D mouse is used to adjust the position of the virtual patient.A multi-threaded computational methodology is adopted to satisfy the requirements of the frame rate.The computation threads mainly consist of the haptic thread running at a frequency of>1000Hz and the graphic thread at>30Hz.The graphic thread allows the graphics engine to effectively display the visual effects of biofilm removal and acid erosion through texture mapping.Using the haptic thread,the physics engine adopts the hierarchy octree collision-detection algorithm to simulate the multi-point and multi-region interaction between the tools and the virtual environment.Its high efficiency guarantees that the time cost can be controlled within 1 ms.The physics engine also performs collision detection between the tools and particles,making it possible to simulate paint and removal of colloids.The surface-contact constraints are defined in the system;this ensures that the bracket will not divorce from or embed into the tooth during the adjustment of the bracket.Therefore,the simulated adjustment is more realistic and natural.Results A virtual system to simulate the complete process of orthodontic bracket bonding was developed.In addition to bracket bonding and adjustment,the system simulates the necessary auxiliary steps such as smearing,acid etching,and washing.Furthermore,the system supports personalized case training.Conclusions The system provides a new method for students to practice orthodontic skills.

Miniature 6-axis force/torque sensor for force feedback in robot-assisted minimally invasive surgery

In order to restore force sensation to robot-assisted minimally invasive surgery(RMIS),design and performance evaluation of a miniature 6-axis force/torque sensor for force feedback is presented.Based on the resistive sensing method,a flexural-hinged Stewart platform is designed as the flexible structure,and a straightforward optimization method considering the force and sensitivity isotropy of the sensor is proposed to determine geometric parameters which are best suited for the given external loads.The accuracy of this method is preliminarily discussed by finite element methods(FEMs).The sensor prototype is fabricated with the development of the electronic system.Calibration and dynamic loading tests for this sensor prototype are carried out.The working ranges of this sensor prototype are 30 N and 300 N·mm,and resolutions are 0.08 N in radial directions,0.25 N in axial direction,and 2.4 N·mm in rotational directions.It also exhibits a good capability for a typical dynamic force sensing at a frequency close to the normal heart rate of an adult.The sensor is compatible with surgical instruments for force feedback in RMIS.

FORCE FEEDBACK MODEL OF ELECTRO-HYDRAULIC SERVO TELE-OPERATION ROBOT BASED ON VELOCITY CONTROL

The tele-operation robotic system which consists of an excavator as the construction robot, and two joysticks for operating the robot from a safe place are useful for performing restoration in damaged areas. In order to accomplish a precise task, the operator needs to feel a realistic sense of task force brought about from a feedback force between the fork glove of slave robot and unfamiliar environment. A novel force feedback model is proposed based on velocity control of cylinder to determine environment force acting on fork glove. Namely, the feedback force is formed by the error of displacement of joystick with velocity and driving force of piston, and the gain is calculated by the driving force and threshold of driving force of hydraulic cylinder. Moreover, the variable gain improved algorithm is developed to overcome the defect for grasping soft object. Experimental results for fork glove freedom of robotic system are provided to demonstrate the developed algorithm is available for grasping soft object.

A Fully Differential Interface Circuit of Closed-loop Accelerometer with Force Feedback Linearization

In this paper,a fifth-order fully differential interface circuit( IC) is presented to improve the noise performance for micromechanical sigma-delta( Σ-Δ) accelerometer. A lead compensator is adopted to ensure the stability of the closed-loop high-order system. A low noise capacitance detection circuit is described with a correlated-double-sampling( CDS) technique to decrease 1 /f noise and offset of the operational amplifier. This paper also proposes a self-test technique for the interface circuit to test the harmonic distortion. An electrostatic force feedback linearization circuit is presented to reduce the harmonic distortion resulting in larger dynamic range( DR). The layout of the IC is implemented in a standard 0. 6 μm CMOS technology and operates at a sampling frequency of 250 kHz. The interface consumes 20 mW from a 5 V supply. The post-simulation results indicate that the noise floor of the digital accelerometer is about- 140 dBV /Hz1 /2at low frequency. The sensitivity is 2. 5 V /g and the nonlinearity is 0. 11%. The self-test function is achieved with 98. 2 dB thirdorder harmonic distortion detection based on the electrostatic force feedback linearization.

A force feedback master finger in exoskeleton type

In order to eliminate the drawbacks of conventional force feedback gloves, a new type of master fin- ger has been developed. By utilizing three ＂four-bar mechanism joint＂ in series and wire coupling mecha- nism, the master finger transmission ratio is kept exactly 1：1.4：1 in the whole movement range and it can make active motions in both extension and flexion directions. Additionally, to assure faster data transmission and near zero delay in the master-slave operation, a digital signal processing/field programmable gate array （DSP/FPGA-FPGA） structure with 200μs cycle time is designed. The operating modes of the master finger can be contact or non-contact, which depends on the motion states of a slave finger, free motion or constrained motion. The position control employed in non-contact mode ensures unconstrained motion and the force control adopted in contact mode guarantees natural contact sensation. To evaluate the performances of the master finger, an experiment between the master finger and a DLR/HTT dexterous finger is conducted. The results demonstrate that this new type master finger can augment telepresence.

Robot Position Control Using Force Information for Cooperative Work in Remote Robot Systems with Force Feedback

This paper proposes robot position control using force information for cooperative work between two remote robot systems with force feedback in each of which a user operates a remote robot by using a haptic interface device while observing work of the robot with a video camera. We also investigate the effect of the proposed control by experiment. As cooperative work, we deal with work in which two robots carry an object together. The robot position control using force information finely adjusts the position of the robot arm to reduce the force applied to the object. Thus, the purpose of the control is to avoid large force so that the object is not broken. In our experiment, we make a comparison among the following three cases in order to clarify how to carry out the control effectively. In the first case, the two robots are operated manually by a user with his/her both hands. In the second case, one robot is operated manually by a user, and the other robot is moved automatically under the proposed control. In the last case, the object is carried directly by a human instead of the robot which is operated by the user in the second case. As a result, experimental results demonstrate that the control can help each system operated manually by the user to carry the object smoothly.

Basic Characteristics of the Hydraulic-Driven Forceps for Force Feedback

A surgical manipulator has widely been used for laparoscopic surgery. It has been chosen mainly for the use in supporting human operations and in robot systems like the da Vinci surgical system. These manipulator systems are suitable for careful work, but they have a few problems. One of the problems is that the manipulator is not equipped with haptic sensing functions. Therefore, the operator must know the advanced techniques for visually detecting the physical contact state during surgical operations. These haptic sensing functions thus need to be incorporated into a surgical manipulator. We have developed hydraulic-driven forceps with a micro bearing and a bellows tube that can convey haptic sense to the operator. This system can measure the small forces acting on the tips of the forceps using Pascal＇s principle. A model of the system is provided from the relationship between the internal pressure of the bellows tube and the refraction angles of the forceps. It was confirmed using this model that the developed system makes it possible to estimate both the strength and the direction of the external force applied to the forceps by measuring the internal pressure of the bellows tube. An operator using a three-dimensional haptic device was able to feel the force response during an experiment in which they used the forceps to hold a blood vessel. This report describes the most appropriate method for letting the operator feel the force conveyed by using our system.

A virtual 3D interactive painting method for Chinese calligraphy and painting based on real-time force feedback technology

A novel 3D interactive painting method for Chinese calligraphy and painting based on force feedback technology is proposed. The relationship between the force exerted on the brush and the resulting brush deformation is analyzed and a spring-mass model is used to build a model of the 3D Chinese brush. The 2D brush footprint between the brush and the plane of the paper or object is calculated according to the deformation of the 3D brush when force is exerted on the 3D brush. Then the 3D brush footprint is obtained by projecting the 2D brush footprint onto the surface of the 3D object in real time, and a complete 3D brushstroke is obtained by superimposing 3D brush footprints along the painting direction. The proposed method has been suc- cessfully applied in a virtual 3D interactive drawing system based on force feedback technology. In this system, users can paint 3D brushstrokes in real time with a Phantom Desktop haptic device, which can effectively serve as a virtual reality interface to the simulated painting environment for users.

Delayed Teleoperation with Force Feedback of a Humanoid Robot

Teleoperation systems allow the extension of human capabilities to remote-control devices by providing the operator with conditions similar to those at the remote site through a communication channel that sends information from one site to the other. This article aims to present an analysis of the benefits of force feedback applied to the bilateral teleoperation of a humanoid robot with timevarying delay. As a control scheme, we link adaptive inverse dynamics compensation, balance control, and P+d like controllers. Finally,a test is performed where an operator simultaneously handles the locomotion(forward velocity and turn angle) and arm of a simulated 3D humanoid robot to do a pick-and-place task using two master devices with force feedback, where indexes such as time to complete the task, coordination errors, path tracking error, and percentage of successful tests are reported for different time-delays. We conclude with the results achieved.

Force-feedback based active compliant position control strategy for a hydraulic quadruped robot

Most existing legged robots are developed under laboratory environments and, corre- spondingly, have good performance of locomotion. The robots＇ ability of walking on rough terrain is of great importance but is seldom achieved. Being compliant to external unperceived impacts is cru- cial since it is unavoidable that the slip, modeling errors and imprecise information of terrain will make planned trajectories to be followed with errors and unpredictable contacts. The impedance control gives an inspiration to realize an active compliance which allows the legged robots to follow reference trajectories and overcome external disturbances. In this paper, a novel impedance force/ position control scheme is presented, which is based on Cartesian force measurement of leg＇ s end effector for our hydraulic quadruped robot The simulation verifies the efficiency of the impedance model, and the experimental results at the end demonstrate the feasibility of the proposed control scheme.

Novel magneto-rheological fluid damper for passive force/torque feedback

The damper is capable of providing a continuously variable dampering force/torque in response to a magnetic field. It consists of an upside cap and an underside cap with a rotor located between them, the magneto-rheological （MR） fluid is filled into the gaps between the rotor and the caps. When the viscosity of the MR fluid increases under the influence of the magnetic field, the movement of the rotor will be resisted. The output torque is made up of the torque caused by the magnetic field, the torque caused by the plastic viscosity of the MR fluid, and the torque caused by the coulomb friction. The viscous torque can be calculated by a simple method and the frictional torque can be obtained by experiments. The torque dependent on the magnetic field is obtained by electromagnetic finite dement analysis. Experiments are done on the damper prototype and the validity of the design is verified.

Force assistant master-slave telerehabilitation robotic system

A prototype of the master slave telerehabilitation robotic system with force feedback is developed. This system contains a pair of robots with the master being operated by the therapist and the slave following the master to guide the patients to exercise. A slave device with a slave controller is designed to stretch and mobilize the impaired elbow joints accurately and safely. A master device with a master controller is designed to control/monitor the procedure of treatment and assess the outcome of treatment remotely and accurately. By using the twoport network theory and the circuit equivalent impedance models, the position-force control scheme is designed to generate force feedback for the therapist who is to be informed of the interaction force between the subject and the robot arm during exercise. Experiments were conducted with a healthy male. Results show that the therapist can guide the patient to exercise by the master arm and can feel the interaction forces between the impaired arm and the robot. Compared with the traditional therapy, this system is more cost-efficient, more convenient and safer for both the stroke patients and the clinicians.

Fuzzy-PID controlled lift feedback fin stabilizer

Conventional PID controllers are widely used in fin stabilizer control systems, but they have time-variations, nonlinearity, and uncertainty influencing their control effects. A lift feedback fuzzy-PID control method was developed to better deal with these problems, and this lift feedback fin stabilizer system was simulated under different sea condition. Test results showed the system has better anti-rolling performance than traditional fin-angle PID control systems.

Safety control strategy for vertebral lamina milling task

Vertebral lamina milling task is one of the high-risk operations in spinal surgeries. The operation is to remove part of vertebral lamina and release the pressure on the spinal nerve. Because many important vessels and nerves are under the vertebral lamina, any incorrect operation may cause irreparable damage to patients. To improve the safety of lamina milling task, a fuzzy force control strategy is proposed in this paper. Primary experiments have been conducted on bone samples from different animals. The results show that, with the fuzzy force control strategy, the bone milling system can recognize all surgery states and halt the tool at the proper location, achieving satisfactory surgery performance.

MODELING OF MICROMANIPULATION ROBOT IN VIRTUAL ENVIRONMENT

Micromanipulation has been recognized to be very difficult due to the inefficiency oftraditional micromanipulation methods. The paper present a general framework formicromanipulation robot based on virtual reality technology. The significance of in-troducing virtual reality into micromanipulation is analyzed, and the current researchin this field is reviewed. Based on this, we propose a micromanipulation system thatintegrates virtual environment with vision feedback and force feedback. The systemrealizes vision close-loop control and force close-loop control to enhance the perfor-mance of micromanipulation device. A graphics modelling method is proposed for amicroassembly task. Hardware and software implementation is described and discus-sion about the research is presented.

Novel Flexible Foot System for Humanoid Robot Adaptable to Uneven Ground

Humanoid robots can walk stably on flat ground, regular slopes, and stairs. However, because of their rigid and flat soles, adapting to unknown rough terrains is limited, moreover, to maintain large scale four-point contact for foot structures to keep balance is usually a key technical problem. In order to solve these problems, the control strategy and foot structures should be improved. In this paper, a novel flexible foot system is proposed. This system occupies 8 degrees of freedom （DOF）, and can obtain larger support region to keep in four-point contact with uneven terrains; Novel cable transmission technology is put forward to reduce complexity of traditional mechanism and control strategy, and variation of each DOF is mapped to cable displacement. Furthermore, kinematics of this new system and a global dynamic model based on contact-force feedback are analyzed. According to stability criterion and feedback sensor information, a method calculating the optimal attitude matrix of contact points and joint variables is introduced. Virtual prototyping models of a 30-DOF humanoid robot and rough terrain are established to simulate humanoid robot walking on uneven ground, and feasibility of this system adapted to uneven terrain and validity of its control strategy are verified. The proposed research enhances the capability of humanoid robots to adapt to large scale uneven ground, expands the application field of humanoid robots, and thus lays a foundation for studies of humanoid robots performing tasks in complex environments in place of humans.