Kinesthetic Force Feedback Research Articles

Variable Stiffness Devices Using Fiber Jamming for Application in Soft Robotics and Wearable Haptics.

Variable stiffness actuation has applications in a wide range of fields, including wearable haptics, soft robots, and minimally invasive surgical devices. There have been numerous design approaches to control and tune stiffness and rigidity; however, most have relatively low specific load-carrying capacities (especially for flexural loads) in the most rigid state that restricts their use in small or slender devices. In this article, we present an approach to the design of slender, high flexural stiffness modules based on the principle of fiber jamming. The proposed fiber jamming modules (FJMs) consist of axially packed fibers in an airtight envelope that transition from a flexible to a rigid beam when a vacuum is created inside the envelope. This FJM can provide the flexural stiffness of up to eight times that of a particle jamming module in the rigid state. Unlike layer jamming modules, the design of FJMs further allows them to control stiffness while bending in space. We present an analytical model to guide the parameter choices for the design of fiber jamming devices. Finally, we demonstrate applications of FJMs, including as a versatile tool, as part of a kinesthetic force feedback haptic glove and as a programmable structure.

Visual Feedback Weakens the Augmentation of Perceived Stiffness by Artificial Skin Stretch.

Tactile stimulation devices are gaining popularity in haptic science and technology-they are lightweight, low-cost, can be wearable, and do not suffer from instability during closed loop interactions with users. Applying tactile stimulation, by means of stretching the fingerpad skin concurrently with kinesthetic force feedback, has been shown to augment the perceived stiffness during interactions with elastic objects. However, to date, the perceptual augmentation due to artificial skin-stretch was studied in the absence of visual feedback. In this article, we tested whether this perceptual augmentation is robust when the stretch is applied in combination with visual displacement feedback. We used a forced-choice stiffness discrimination task with four conditions: force feedback, force feedback with skin-stretch, force and visual feedback, and force and visual feedback with skin-stretch. We found that the visual feedback weakens, but does not eliminate, the skin-stretch induced perceptual effect. Additionally, no effect of visual feedback on the discrimination precision was found.

The Treadport: Natural Gait on a Treadmill

To evaluate the differences between walking on an advanced robotic locomotion interface called the Treadport and walking overground with healthy subjects. Previous studies have compared treadmill-based and overground walking in terms of gait parameters. The Treadport's unique features including self-selected speed capability, large belt, kinesthetic force feedback, and virtual reality environment distinguish it from other locomotion interfaces and could provide a natural walking experience for the users. Young, healthy subjects (N = 17) walked 10 meters 10 times each for both overground and the Treadport environments. Comparison between walking conditions used spatiotemporal and kinematic parameters. In addition, electromyographic data was collected for five of the 17 subjects to compare muscle activity between the two conditions. Gait on the Treadport was found to have no significant differences (p > .05) with overground walking in terms of hip and knee joint angles, cadence and stride length and stride speed, and muscle activation of the four muscle groups measured. Differences (p < .05) were observed in ankle dorsiflexion which was reduced by 2.47 ± 0.01 degrees on the Treadport. Walking overground and on the Treadport is highly correlated and not significantly different in 13 of 14 parameters. This study suggests that the Treadport creates an environment for natural walking experience, where natural gait of users is almost preserved, with great potential to be useful for other applications, such as gait rehabilitation of individuals with walking impairments.

Comparison Between Force-Controlled Skin Deformation Feedback and Hand-Grounded Kinesthetic Force Feedback for Sensory Substitution

Teleoperation and virtual reality systems benefit from force sensory substitution when kinesthetic force feedback devices are infeasible due to stability or workspace limitations. We compared the performance of sensory substitution when it is provided through a cutaneous method (skin deformation feedback) and a kinesthetic method (hand-grounded force feedback). For skin deformation feedback, we used a new force-controlled tactile sensory substitution device with the ability to provide tangential and normal force directly to the finger pad. Three-axis force control with 15 Hz bandwidth was achieved using a delta mechanism and three-axis force sensor. For hand-grounded force feedback, forces were grounded against the palm. As a control, world-grounded force feedback was provided using a three-degree-of-freedom kinesthetic force feedback device. Study participants were able to match a reference world-grounded force better with hand-grounded kinesthetic force feedback than with skin deformation feedback. Participants were also able to apply more accurate and precise forces with hand-grounded kinesthetic force feedback than with skin deformation feedback. Conversely, skin deformation feedback resulted in the lowest error during initial force adjustment. These experiments demonstrate relative advantages and disadvantages of skin deformation and hand-grounded kinesthetic force feedback for force sensory substitution.

Three-Dimensional Skin Deformation as Force Substitution: Wearable Device Design and Performance During Haptic Exploration of Virtual Environments.

Virtual reality systems would benefit from a compelling force sensory substitute when workspace or stability limitations prevent the use of kinesthetic force feedback systems. We present a wearable fingertip haptic device with the ability to make and break contact in addition to rendering both shear and normal skin deformation to the fingerpad. A delta mechanism with novel bias spring and tether actuator relocation method enables the use of high-end motors and encoders, allowing precise device control: 10 Hz bandwidth and 0.255 mm RMS tracking error were achieved during testing. In the first of two experiments, participants determined the orientation of a stiff region in a surrounding compliant virtual surface with an average angular error of 7.6 degree, similar to that found in previous studies using traditional force feedback. In the second experiment, we evaluated participants' ability to interpret differences in friction. The Just Noticeable Difference (JND) of surface friction coefficient discrimination using our skin deformation device was 0.20, corresponding with a reference friction coefficient of 0.5. While higher than that found using kinesthetic feedback, this demonstrates that users can perceive differences in surface friction without world-grounded kinesthetic forces. These experiments show that three DoF skin deformation enables both stiffness and friction discrimination capability in the absence of kinesthetic force feedback.

An autoclavable wireless palpation instrument for minimally invasive surgery.

Minimally invasive surgery prevents surgeons from manually palpating organs to locate subsurface tumors and other structures. One solution is to use ultrasound; however, it is not always reliable. Various minimally invasive surgery instruments that provide tactile feedback have been proposed to augment ultrasound sensing for tumor localization; however, current designs have limitations such as cumbersome wiring, difficulty in manipulation, lack of sterilizability and high cost. This paper presents a novel, autoclavable, wireless, hand-held palpation instrument that uses a custom, low-cost, disposable tactile sensor to provide tactile and kinesthetic force feedback. The use of a replaceable, disposable tactile sensor avoids deterioration in sensor performance due to repeated autoclaving. The instrument features a passive joint in the end effector that allows the sensor to self-align to the palpation surface in a wide range of orientations. All of the electronics are packaged in a removable module that allows the rest of the instrument to be easily cleaned and autoclaved. Two versions of the tactile sensor, using piezoresistive sensing and capacitive sensing respectively, have been designed for use with this instrument. The instrument is shown to be able to detect 6 mm diameter spherical tumors at a depth of 9-10 mm in ex vivo tissue samples.

Tactor-Induced Skin Stretch as a Sensory Substitution Method in Teleoperated Palpation

When we use a tool to explore or manipulate an object, friction between the surface of the tool and the fingerpads generates skin stretch cues that are related to the interaction forces between the tool and the object. In this study, we emulate these naturally occurring skin stretch cues in order to convey force direction and magnitude information to users during teleoperation. We hypothesize that skin stretch feedback is a useful substitute for kinesthetic force feedback in force-sensitive teleoperated tasks. In this study, ten participants performed teleoperated palpation to determine the orientation of a stiff region in a surrounding artificial tissue using five feedback conditions: skin stretch, force, reduced gain force, graphic, and vibration. When participants received skin stretch feedback, they localized the stiff region as well as with force feedback, with no increase in task completion time. Additionally, participants receiving skin-stretch feedback localized the stiff region statistically significantly more accurately than those using vibration feedback. Although participants using skin stretch exhibited higher interaction forces than when using force, vibration, and graphical feedback, skin stretch statistically significantly decreased interaction forces compared with reduced gain force feedback. Thus, skin-stretch feedback is a compelling substitute for force feedback and may be useful in scenarios where force feedback is reduced or infeasible.

Kinesthetic Force Feedback and Belt Control for the Treadport Locomotion Interface.

This paper describes an improved control system for the Treadport immersive locomotion interface, with results that generalize to any treadmill that utilizes an actuated tether to enable self-selected walking speed. A new belt controller is implemented to regulate the user's position; when combined with the user's own volition, this controller also enables the user to naturally self-select their walking speed as they would when walking over ground. A new kinesthetic-force-feedback controller is designed for the tether that applies forces to the user's torso. This new controller is derived based on maintaining the user's sense of balance during belt acceleration, rather than by rendering an inertial force as was done in our prior work. Based on the results of a human-subjects study, the improvements in both controllers significantly contribute to an improved perception of realistic walking on the Treadport. The improved control system uses intuitive dynamic-system and anatomical parameters and requires no ad hoc gain tuning. The control system simply requires three measurements to be made for a given user: the user's mass, the user's height, and the height of the tether attachment point on the user's torso.

Improving Transparency in Teleoperation by Means of Cutaneous Tactile Force Feedback

A study on the role of cutaneous and kinesthetic force feedback in teleoperation is presented. Cutaneous cues provide less transparency than kinesthetic force, but they do not affect the stability of the teleoperation system. On the other hand, kinesthesia provides a compelling illusion of telepresence but affects the stability of the haptic loop. However, when employing common grounded haptic interfaces, it is not possible to independently control the cutaneous and kinesthetic components of the interaction. For this reason, many control techniques ensure a stable interaction by scaling down both kinesthetic and cutaneous force feedback, even though acting on the cutaneous channel is not necessary.We discuss here the feasibility of a novel approach. It aims at improving the realism of the haptic rendering, while preserving its stability, by modulating cutaneous force to compensate for a lack of kinesthesia. We carried out two teleoperation experiments, evaluating (1) the role of cutaneous stimuli when reducing kinesthesia and (2) the extent to which an overactuation of the cutaneous channel can fully compensate for a lack of kinesthetic force feedback. Results showed that, to some extent, it is possible to compensate for a lack of kinesthesia with the aforementioned technique, without significant performance degradation. Moreover, users showed a high comfort level in using the proposed system.

Virtual prototyping of mechanical systems with tool mediated haptic feedback

Haptic feedback usually involves two types of stimulation forces: forces that address the touch sense and forces that address the kinesthetic perception. Touch forces have a low intensity and a complex structure since they reflect contact phenomena where friction plays an important role. Therefore, they are quite difficult to simulate. Virtual prototyping with haptic feedback should ideally involve both types of forces, but the integration of the touch feeling makes the simulator very complex. In this paper, we present a novel concept for virtual prototyping in which the touch interaction is separated from the kinesthetic force feedback. This is possible using a prototype that has a real part undertaking the touch interaction and a virtual part that simulate feedback for the kinesthetic forces. In this way, a full haptic interaction with the virtual prototype is established by means of a device that provides a realistic simulation of the product. In order to illustrate the concept, several experiments have been carried out for the case of specific subsystems of a car, which are particularly involved in the driver---car interaction: steering system, clutch pedal and the gearshift. A user test is described in the last part as well as the conclusions of the research.

Cutaneous Force Feedback as a Sensory Subtraction Technique in Haptics.

A novel sensory substitution technique is presented. Kinesthetic and cutaneous force feedback are substituted by cutaneous feedback (CF) only, provided by two wearable devices able to apply forces to the index finger and the thumb, while holding a handle during a teleoperation task. The force pattern, fed back to the user while using the cutaneous devices, is similar, in terms of intensity and area of application, to the cutaneous force pattern applied to the finger pad while interacting with a haptic device providing both cutaneous and kinesthetic force feedback. The pattern generated using the cutaneous devices can be thought as a subtraction between the complete haptic feedback (HF) and the kinesthetic part of it. For this reason, we refer to this approach as sensory subtraction instead of sensory substitution. A needle insertion scenario is considered to validate the approach. The haptic device is connected to a virtual environment simulating a needle insertion task. Experiments show that the perception of inserting a needle using the cutaneous-only force feedback is nearly indistinguishable from the one felt by the user while using both cutaneous and kinesthetic feedback. As most of the sensory substitution approaches, the proposed sensory subtraction technique also has the advantage of not suffering from stability issues of teleoperation systems due, for instance, to communication delays. Moreover, experiments show that the sensory subtraction technique outperforms sensory substitution with more conventional visual feedback (VF).

Force and Contact Location Shading Methods for Use Within Two- and Three-Dimensional Polygonal Environments

Current state-of-the-art haptic interfaces only provide kinesthetic (force) feedback, yet studies have shown that providing tactile feedback in concert with kinesthetic information can dramatically improve a person's ability to dexterously interact with and explore virtual environments. In this research, tactile feedback was provided by a device, called a contact location display (CLD), which is capable of rendering the center of contact to a user. The chief goal of the present work was to develop algorithms that allow the CLD to be used with polygonal geometric models, and to do this without the resulting contact location feedback being overwhelmed by the perception of polygonal edges and vertices. Two haptic shading algorithms were developed to address this issue and successfully extend the use of the CLD to 2D and 3D polygonal environments. Two experiments were run to evaluate these haptic shading algorithms. The first measured perception thresholds for rendering faceted objects as smooth objects. It was found that the addition of contact location feedback significantly increased user sensitivity to edges and that the use of shading algorithms was able to significantly reduce the number of polygons needed for objects to feel smooth. The second experiment explored the CLD device's ability to facilitate exploration and shape recognition within a 3D environment. While this study provided a validation of our 3D algorithm, as people were able to identify the rendered objects with reasonable accuracy, this study underscored the need for improvements in the CLD device design in order to be effectively used in general 3D environments.

Physical Interaction with a Virtual Knee Joint—The 9 DOF Haptic Display of the Munich Knee Joint Simulator

In specific fields, medical education at many universities is rather theoretical and the amount of practical training is limited. A significant improvement can be achieved using virtual reality training stations with lifelike visual, acoustic, tactile, and kinesthetic feedback. Particularly, when simulating procedures that require direct contact with the patient body, a realistic haptic simulation addressing tactile and kinesthetic senses can be essential for the acceptance of virtual simulation stations. A purely passive phantom may provide realistic haptic feedback, but its properties cannot be changed over time. This paper presents the haptic display of the Munich Knee Joint Simulator, which was developed to improve training and education of physical knee joint examinations. The haptic interface comprises a combination of passive phantom segments providing realistic tactile sensations, and strong actuators generating highly dynamic kinesthetic force feedback. A 3 degree of freedom (DOF) manipulator was developed in this study to drive the thigh prosthesis and one 6 DOF industrial robot was used to actuate the shank prosthesis. Both manipulators are driven by hybrid admittance-impedance controllers capable of simulating the complex dynamics of the thigh and the shank. Both actuators are equipped with a 6 DOF force torque sensor and they are virtually coupled by an analytical knee joint model. The proposed setup is capable of simulating a mechanical stiffness as high as 80 kN/m in the translatory DOF and simultaneously allows free motion in the rotatory DOF. Experimental tests of the simulator with orthopedic physicians proved the usability of the proposed concept.

질감 제시 장치를 이용한 촉감인지 특성 연구

This paper describes three kinds of experiments and analysis of their results related to human tactile sensitivity using an integrated tactile display system. The device can provide vibration, normal pressure and lateral slip/stretch which are important physical quantities to sense texture. We have tried to find out the efficient method of stimulating, limitation of surface discrimination by kinesthetic farce feedback and the effectiveness of the combination of kinesthetic force and tactile feedback. Seven kinds of different stimulating methods were carried out and they are single or combination of the kinesthetic force, normal static pressure, vibration, active/passive shear and moving wave. Both prototype specimen and stimulus using tactile display were provided to all examinees and they were allowed to answer the most similar sample. The experimental results show that static pressure is proper stimulus for the display of micro shape of the surface and vibrating stimulus is more effective for the display of fine surface. And the sensitivities of active touch and passive touch are compared. Since kinesthetic force feedback is appropriate to display shape and stiffness of an object, but roughness display has a limitation of resolution, the concurrent providing methods of kinesthetic and tactile feedback are applied to simulate physical properties during touching an object.

Ground–Space Bilateral Teleoperation of ETS-VII Robot Arm by Direct Bilateral Coupling Under 7-s Time Delay Condition

A bilateral teleoperation experiment with Engineering Test Satellite 7 (ETS-VII) was conducted on November 22, 1999. Round-trip time for communication between the National Space Development Agency of Japan ground station and the ETS-VII was approximately seven seconds. We constructed a bilateral teleoperator that is stable, even under such a long time delay. Several experiments, such as slope-tracing task and peg-in-hole task, were carried out. Task performance was compared between the bilateral mode and the unilateral mode with force telemetry data visually displayed on a screen. All tasks were possible by bilateral control without any visual information. Experimental results showed that kinesthetic force feedback to the operator is helpful even under such a long time delay, and improves the performance of the task.

The effect of sensory feedback on the identification of objects using a teleoperator

In this work, we are concerned with the role that the haptic system plays in teleoperation i.e. the exploration and manipulation of objects by a human operator using a remote robot arm. The approach is to incrementaly enhance the remote touch-sensing capability beyond kinesthetic force feedback to include contact data and local re-perception and compare the time to identify quasi-two dimensional objects with that of a directly held probe. Results obtained indicated that action between the remote probe and the environment made the force feedback signal “noisy” leading to conflicting and inaccurate hypotheses by the operators. Sensory feedback improved the signal to noise ratio giving performance levels approaching those of direct, as opposed to remote probing.

Force-reflection and shared compliant control in operating telemanipulators with time delay

Shared compliant control has been incorporated into an advanced six-degree-of-freedom force-reflecting telemanipulation system. With this system the authors have investigated the effect of time delay on human telemanipulation task performance. Time delays of between 2 and 4096 ms were introduced between master and slave arms, and high-precision peg-in-hole tasks were performed by six test operators with two modes of control: kinesthetic force feedback (KFF) and shared compliant control (SCC). Task performance was quantified in terms of the completion time (CT) and the sum of square forces (SOSF). The experimental results demonstrate the superiority of SCC over KFF for time-delayed telemanipulation. SCC has significantly lower rates of increase than KFF in both CT and SOSF with time delay. Only SCC enabled task performance at delays above 1 s. Constant force maintenance tasks were also performed to investigate the effect of time delay on the stability of force reflection. SCC also has beneficial effects on telemanipulation without time delay. >

Perception of two-dimensional shapes using haptic feedback

In this work, we are concerned with the role that the haptic system plays in teleoperation, i.e. the exploration and manipulation of objects by a human operator using a remote robot arm. The approach is to incrementally enhance the remote touch-sensing capability beyond kinesthetic force feedback to include contact data and local re-perception and compare the time to identify quasi two-dimensional objects with that of a directly held probe. Results obtained indicated that friction between the remote probe and the environment made the feedback signal ‘noisy’ leading to conflicting and inaccurate hypotheses by the operators. Sensory feedback improved the signal-to-noise ratio giving performance levels approaching those of direct, as opposed to remote, probing.