Design and Control of a Force-Reflecting Haptic Interface for Teleoperational Grasping

A haptic interface is a device for operators to touch, feel and manipulate virtual environments. It senses the contact forces and gives operators a sensation of interacting with a real physical environment. Force feedback can improve the quality of the haptic feedback control in virtual reality applications. In this paper, a real time haptic interface is developed via control models in the Labview virtual environment, which is a combination of a touch force measurement haptic interface and a vibro-tactile CyberGlove serial haptic interface. The haptic interface is a prototype for real time feedback control on robotic integration of smart censors. This approach is easy to apply on various types of sensors, such as acoustic wave sensors, ultrasound array, etc., which will enhance the ability to communicate between the operators and the virtual environment. The flexiforce sensor and tactile sensor based haptic interface in force feedback systems will improve traditional robot visual sensing systems by a virtual feel.

Haptic User Interface for a Telerobotic System – Design based on a Network Model

Vitreo-retinal surgery encompasses the surgical procedures performed on the vitreous humor and the retina. A procedure typically consists of the removal of the vitreous humor, the peeling of a membrane and/or the repair of a retinal detachment. Operations are performed with needle shaped instruments which enter the eye through surgeon made scleral openings. An instrument is moved by hand in four degrees of freedom (three rotations and one translation) through this opening. Two rotations (? and ? ) are for a lateral instrument tip movement. The other two DoFs (z and ?) are the translation and rotation along the instrument axis. Actuation of for example a forceps can be considered as a fifth DoF. Characteristically, the manipulation of delicate, micrometer range thick intraocular tissue is required. Today, eye surgery is performed with a maximum of two instruments simultaneously. The surgeon relies on visual feedback only, since instrument forces are below the human detection limit. A microscope provides the visual feedback. It forces the surgeon to work in a static and non ergonomic body posture. Although the surgeon’s proficiency improves throughout his career, hand tremor may become a problem around his mid-fifties. Robotically assisted surgery with a master-slave system enhances dexterity. The slave with instrument manipulators is placed over the eye. The surgeon controls the instrument manipulators via haptic interfaces at the master. The master and slave are connected by electronic hardware and control software. Implementation of tremor filtering in the control software and downscaling of the hand motion allow prolongation of the surgeon’s career. Furthermore, it becomes possible to do tasks like intraocular cannulation which can not be done by manually performed surgery. This thesis focusses on the master console. Eye surgery procedures are observed in the operating room of different hospitals to gain insight in the requirements for the master. The master console as designed has an adjustable frame, a 3D display and two haptic interfaces with a coarse adjustment arm each. The console is mounted at the head of the operating table and is combined with the slave. It is compact, easy to place and allows the surgeon to have a direct view on and a physical contact with the patient. Furthermore, it fits in today’s manual surgery arrangement. Each haptic interface has the same five degrees of freedom as the instrument inside the eye. Through these interfaces, the surgeon can feel the augmented instrument forces. Downscaling of the hand motion results in a more accurate instrument movement compared to manually performed surgery. Together with the visual feedback, it is like the surgeon grasps the instrument near the tip inside the eye. The similarity between hand motion and motion of the instrument tip as seen on the display results in an intuitive manipulation. Pre-adjustment of the interface is done via the coarse adjustment arm. Mode switching enables to control three or more instruments manipulators with only two interfaces. Two one degree of freedom master-slave systems with force feedback are built to derive the requirements for the haptic interface. Hardware in the loop testing provides valuable insights and shows the possibility of force feedback without the use of force sensors. Two five DoF haptic interfaces are realized for bimanual operation. Each DoF has a position encoder and a force feedback motor. A correct representation of the upscaled instrument forces is only possible if the disturbance forces are low. Actuators are therefore mounted to the fixed world or in the neighborhood of the pivoting point for a low contribution to the inertia. The use of direct drive for ' and and low geared, backdriveable transmissions for the other three DoFs gives a minimum of friction. Disturbance forces are further minimized by a proper cable layout and actuator-amplifier combinations without torque ripple. The similarity in DoFs between vitreo-retinal eye surgery and minimally invasive surgery (MIS) enables the system to be used for MIS as well. Experiments in combination with a slave robot for laparoscopic and thoracoscopic surgery show that an instrument can be manipulated in a comfortable and intuitive way. User experience of surgeons and others is utilized to improve the haptic interface further. A parallel instead of a serial actuation concept for the ' and DoFs reduces the inertia, eliminates the flexible cable connection between frame and motor and allows that the heat of the motor is transferred directly to the frame. A newly designed z-?? module combines the actuation and suspension of the hand held part of the interface and has a three times larger z range than in the first design of the haptic interface.

In this paper, bilateral control with two degrees of freedom (2-DOF) haptic spherical interface is proposed. There is much research about the mechanical structure of the haptic interface to realize large movable range. However, these are not suitable for the interface of the open environment. In addition, to achieve wide movable range, there are some problems that the robot gets large and the large inertia deteriorates the operationality according to the movable range. In this paper, by utilizing a sphere as a interface, the interface has the two degrees of freedom and the unlimited movable range. The interface is utilized as the master robot. Meanwhile, an X-Y stage is utilized as the slave robot. The number of the actuators, the actuator type, and the structures are different between master-slave robots. Hence, bilateral control considering the differences is proposed.

In this study, the developed 7-DOF haptic device (HaP-7) and its virtual reality interface are presented. The design issues, design constraints, and alternative design configurations are discussed and the potential advantages of the HaP-7 are put forward. The kinematic model of the proposed device looks like a simplified human arm kinematic model. The redundant characteristic of the device provides larger workspace and allows for appropriate posture selection for the purposes of maximization of the rigidity, transparency and stability, while minimizing the inertia and power consumption in addition to the singularity and obstacle avoidance optimization.

As robotics prehension systems and virtual reality applications are in constant evolution, the need for high-fidelity haptic interaction increases. This helps ensure and enhance user immersion and handling precision. While commercial haptic interfaces offer high performance, their prohibitive cost limits their widespread adoption in general-purpose robotics. Furthermore, many low-cost solutions suffer from limited transparency, where the operator constantly fights the friction of the actuator even during free motion. This article presents the design and development of an innovative, cost-effective master-slave robotic system aimed at democratizing efficient haptic feedback devices. The solution is intended for remote manipulation of objects with a maximum mass of 1 kg, while limiting the gripping force to 50 N, thus ensuring the integrity of objects being manipulated. The device includes a master haptic module in the form of a clamp that reproduces the thumb-index-middle finger gripping motion performed by the user. The system relies on a custom haptic interface measuring the angular position of the master gripper, which is transmitted in real time to the slave gripper, so as to adjust the position of the clamp accordingly, thus optimizing the grasping control loop. As soon as an object is detected, using a force sensor integrated into the slave gripper, the master motor renders a resistive force, preventing the user from closing the haptic module. The other part of the system is the slave mechanical gripper with three fingers, each with three phalanges based on human anatomy, allowing the clamp to mechanically conform to irregular object geometries with a single actuator. The last but not least innovative aspect lies in the implementation of a current sensor, which provides the haptic feedback. The force applied by the user is reproduced by the slave gripper using current sensors, eliminating the need for expensive force-torque sensors while maintaining a responsive feedback loop.

This paper presents a compact-sized haptic device based on a cable-driven parallel robot (CDPR) mechanism for teleoperation. CDPRs characteristically have large workspaces and lightweight actuators. An intuitive and user-friendly remote control has not yet been achieved, owing to the unfamiliar multiple-cable configuration of CDPRs. To address this, we constructed a portable compact-sized CDPR with the same configuration as that of a larger fully constrained slave CDPR. The haptic device is controlled by an admittance control for stiffness adjustment and implemented in an embedded microprocessor-based controller for easy installation on an operator’s desk. To validate the performance of the device, we constructed an experimental teleoperation setup by using the prototyped portable CDPR as a master and larger-size CDPR as a slave robot. Experimental results showed that a human operator can successfully control the master device from a remote site and synchronized motion between the master and slave device was performed. Moreover, the user-friendly teleoperation could intuitively address situations at a remote site and provide an operator with realistic force during the motion of the slave CDPR.

Force feedback from the virtual world can greatly enhance the sense of immersion even for simple applications. The ISU force reflecting exoskeleton enables the user to interact dynamically with simulated environments by providing an electromagnetic haptic interface between the human and the environment. The paper describes the high bandwidth electromagnetic haptic interface and how it has been used to provide the sense of contact in the synthetic environment. The air gap between the magnetics, carried by the robot, and the coils attached to the human's digits, allows for small relative motion between the human and the robot without affecting the transmission of forces. This flexibility allows the robot to track the human as well as develop appropriate forces from the virtual world. Three different typical synthetic environments are programmed and tested using the ISU force reflecting exoskeleton haptic interface device. The experimental results shows that the magnetic interface gives adequate force levels for perception of virtual objects, enhancing the feeling of immersion in the virtual environment.

We present the design, analysis, control and characterization of a general purpose, six degrees-of-freedom (DoF) haptic interface for the rendering of elements and interior equipment like sliders, drawers, eyeglass holders or gloveboxes in a car. One of the major challenges in the design of six DoF haptic interfaces is the trade-off between workspace size, stiffness, output capability, and bandwidth. In order to meet this challenge we propose a new kinematic structure that allows to cover a relatively large workspace in both rotational and translational degrees of freedom, while ensuring high velocity and force output capabilities to render a wide range of impedances. An admittance controller with model-based gravity and Coriolis compensation is implemented to render different types of elements and interior equipment in a car. Hardware-related performance measures like dexterous workspace and output capabilities are derived based on kinematic and dynamic simulations and are compared to state-of-the-art devices.

This paper presents the design and characteristics of a five-fingered haptic interface robot: HIRO III. The aim of the paper is to provide a high-precision force representation at the five human fingertips. HIRO III consists of a 15-degree-of-freedom (DOF) haptic hand, a 6 DOF interface arm and a control system. The haptic interface, which consists of a robot arm and hand, can be used in a large workspace and can provide multipoint contact between the user and a virtual environment. However, the following problems peculiar to a multi-DOF robot have resulted: a backlash, a large amount of friction, many motors, and many sensors. In order to solve these problems, a new mechanism and a wire-saving control system have been designed and developed. Furthermore, experiments in both free space and constraint space have been carried out. In comparison with the previous HIRO, the force errors in free space and in constraint space have been reduced to 30% and 57%, respectively. These results show a high-precision force representation and the great potential of HIRO III.

This paper presents an efficient force position control scheme for high precision drilling on soft surfaces using industrial robot. The control problem is divided into two parts; the gross motion control problem and the drilling control problem. In the gross motion stage the robot motion is controlled using computed torque technique. The drilling process is controlled using hybrid force position control that maintains the desired force and trajectory profiles. The soft surface is represented by single degree of freedom mass-spring-damper system. The performance of the system is tested using 6-dof PUMA 560 robot model.

This paper presents a frequency-dependent digital damping referred to a digital input shaper (DIS). Compared to the previously proposed analog input shaper, the DIS makes the implementation of damping much more flexible and significantly reduces the electrical noise. Moreover, the DIS can incorporate position control at the initial contact with virtual objects to improve the perceived contact hardness. Through benchmark virtual wall experiments, we show that the DIS can significantly increase the impedance range that a haptic interface can stably display, and that the initial contact hardness that a user perceives can be noticeably improved by using the proposed position control method.

The sense of touch is essential to perform discriminating tasks in virtual reality applications or virtual training systems. To discriminate between different virtual objects, a human operator needs to clearly perceive the stiffness of each object. Stiffness is not only a material property, but also a characteristic of the particular object and express how it is being touched. Stiffness affects the perception of surface topography and depends on the area of applied force. While haptic-enabled virtual reality training systems have been received considerable attention in recent years, our main criticism on these systems is that their virtual environments provide homogeneous haptic stiffness and less perceptually accurate virtual space. This paper investigated how texture affects the perception of haptic stiffness of the virtual object. By performing a psychophysical experiment, we determined that human operator' average accuracy in discriminating perceived haptic stiffness of the virtual object is depending on its texture information and spatial variations. Our findings underscore the importance of implementing spatially varying haptic parameters.

This paper presents a quantitative characterization of the instability that a human user often experiences while interacting with a virtual textured surface rendered with a force-reflecting haptic interface. First, we quantified the degree of stability/ instability during haptic texture rendering through psychophysical experiments. The stiffness of the virtual textured surface upon detection of instability was measured under a variety of experimental conditions using two texture rendering methods, two exploration modes, and various texture model parameters. We found that the range of stiffness values for stable texture rendering was quite limited. Second, we investigated the attributes of the proximal stimuli experienced by a human hand while exploring the virtual textured surface in an attempt to identify the sources of perceived instability. Position, force, and acceleration were measured and then analyzed in the frequency domain. The results were characterized by sensation levels in terms of spectral intensity in dB relative to the human detection threshold at the same frequency. We found that the spectral bands responsible for texture and instability perception were well separated in frequency such that they excited different mechanoreceptors and were, therefore, perceptually distinctive. Furthermore, we identified the high-frequency dynamics of the device to be a likely source of perceived instability. Our work has implications for displaying textured surfaces through a force feedback device in a virtual environment.

Improvements on the wearable fingernail sensor are presented. By measuring changes in the color pattern of the human fingernail, the sensor is capable of detecting finger posture as well as touch forces which are applied to the fingertip. The fingernail is instrumented with a fitted sensor containing arrays of miniature LEDs and photodiodes that measure the blood content underneath the nail. Dynamic pattern recognition is used to differentiate between changes due to touching and bending. Since the sensor is mounted on the fingernail, touch forces can be measured without covering the fingerpad and obstructing the human’s natural haptic sense. Similarly, finger bending can be measured without wearing a glove that hampers the motion of the fingers. This paper briefly discusses design of the sensors, and then demonstrates sensor capabilities for both touch force and posture measurement.