Force Perception Research Articles

Higher variability in cervical force perception in people with neck pain

BackgroundA reduced capacity to generate and sustain cervical muscle force over a range of contraction intensities is a feature of some participants with neck pain. To date there have been no studies comparing the accuracy of force perception in participants with and without neck pain. DesignCross-sectional observational study. MethodsParticipants with (n = 25) and without (n = 25) neck pain performed isometric muscle contractions at three progressive self-perceived (no feedback provided) intensities (10, 25, 50) % of their maximal voluntary contraction (MVC) in cervical: flexion, extension, right and left lateral flexion. Absolute error (AE), constant error (CE), and variable error (VE) between actual and targeted force values were calculated. ResultsThe neck pain group had: (1) AE-combined direction -significantly higher at 10% and lower at 50% (p < 0.05); (2) significantly lower CE in most measures (p < 0.05); (3) higher mean VE in all measures, with 10, 25, and 50% combined direction and overall combined % extension significantly higher (p < 0.05). ConclusionsFindings indicate higher variability in force generation perception across all directions and intensities in participants with neck pain compared to healthy controls. Potentially this greater variability might suggest impaired force sense, a construct of proprioception in participants with neck pain. Reduced force sense may have implications for participants with neck pain during functional activities requiring precision and may need to be trained. Further research is required.

Haptic interface using tendon electrical stimulation with consideration of multimodal presentation

Background Our previous studies have shown that electrical stimulation from the skin surface to the tendon region (Tendon Electrical Stimulation: TES) can elicit a force sensation, and adjusting the current parameters can control the amount of the sensation. TES is thought to present a proprioceptive force sensation by stimulating receptors or sensory nerves responsible for recognizing the magnitude of the muscle contraction existing inside the tendon, so it can be a proprioceptive module of a small-size, low-cost force feedback device. But there is also suspect that TES presents only strong, noisy skin sensation. From previous study, it was found that TES has some limitation on varying sensations. Methods In this study, in addition to characterizing the proprioceptive sensation induced by TES, we constructed a multimodal presentation system reproducing a situation in which force is applied to the hand was offered, so as to investigate whether TES contributed to the reproduction of haptics cooperating with other modalities, rather than disturbing them. Specifically, we used vibration to present a cutaneous sensation and a visual head mounted display (HMD) system to present simultaneous images. Using this system, we also evaluated the efficacy of TES itself and that of the multimodal system involving TES. Results We found that TES, along with visual and vibration stimulation, contributed to the perception of a certain force. Conclusions Thus, TES appears to be an effective component of multimodal force sense presentation systems.

Sclera Force Control in Robot-assisted Eye Surgery: Adaptive Force Control vs. Auditory Feedback.

Surgeon hand tremor limits human capability during microsurgical procedures such as those that treat the eye. In contrast, elimination of hand tremor through the introduction of microsurgical robots diminishes the surgeons tactile perception of useful and familiar tool-to-sclera forces. While the large mass and inertia of eye surgical robot prevents surgeon microtremor, loss of perception of small scleral forces may put the sclera at risk of injury. In this paper, we have applied and compared two different methods to assure the safety of sclera tissue during robot-assisted eye surgery. In the active control method, an adaptive force control strategy is implemented on the Steady-Hand Eye Robot in order to control the magnitude of scleral forces when they exceed safe boundaries. This autonomous force compensation is then compared to a passive force control method in which the surgeon performs manual adjustments in response to the provided audio feedback proportional to the magnitude of sclera force. A pilot study with three users indicate that the active control method is potentially more efficient.

Application of a Redundant Haptic Interface in Enhancing Soft-Tissue Stiffness Discrimination

Haptic-enabled teleoperated surgical systems have the potential to enhance the accuracy and performance of surgical interventions. The user interface of such a system can provide haptic feedback to the surgeon to more intuitively perform surgical tasks. In this letter, we study the added benefits of redundant manipulators as haptic interfaces for teleoperated surgical systems. First, we introduce the intrinsic benefits of employing a redundant haptic interface, namely, reduced apparent inertia and increased manipulability (one result of which is reduced friction forces). Next, we demonstrate that the haptic interface redundancy can further reduce its apparent inertia and friction via appropriately manipulating the extra degrees of freedom of the interface. This will consequently enhance the haptic feedback resolution (sensitivity) for the user. Finally, a psychophysical experiment is performed to validate the improved force perception for the user in a virtual soft-tissue palpation task. We conduct a set of perceptual experiments to evaluate how a redundant and non-redundant user interface affects the perception of the virtual stiffness. Experimental results demonstrate that the redundancy in the haptic user interface helps to enhance tissue stiffness discrimination ability of the user by reducing the distortions caused by the kinematics and dynamics of the user interface.

Force perception at the shoulder after a unilateral suprascapular nerve block.

There are two key sources of information that can be used to match forces-the centrally generated sense of effort and afferent signals from mechanical receptors located in peripheral tissues. There is currently no consensus on which source of information is more important for matching forces. The corollary discharge hypothesis argues that subjects match forces using the centrally generated sense of effort. The purpose of this study was to investigate force matching at the shoulder before and after a suprascapular nerve block. The nerve block creates a sensory and muscle force mismatch between sides when matching loads. The torque matching accuracy did not change after the nerve block was administered. Directionally, the torque error was in the direction proposed by the corollary discharge hypothesis. However, the mismatch between deltoid EMG was substantially greater compared to the changes in the torque matching error after the block. The results support that sensory information is used during force matching tasks. However, since the nerve block also created a sensory disruption between sides, it is not clear how sensory information is reweighted following the nerve block and a role for sense of effort is still implicated.

Effectiveness of an on-body lifting aid (HAL® for care support) to reduce lower back muscle activity during repetitive lifting tasks

The Hybrid Assistive Limb Lumbar Type (HAL) is an active exoskeleton that provides motion according to the wearer’s voluntary drive. It was developed to support back muscles during repetitive lifting tasks. The purpose of this paper was to determine if the myoelectric activity of the back muscles is reduced or altered when using the HAL and to investigate a possible influence of its use on the cardiovascular system. Fourteen healthy young men without lower back pain underwent a freestyle, symmetrical-lifting protocol. Participants lifted a 17.05 kg handled-box for 10 min. with and without HAL support. Surface electromyography (sEMG) signals were recorded at thoracic (TES) and lumbar erector spinae (LES) and quadriceps femoris (QF). Heart rate was recorded from electrocardiogram. The subjects rated their level of physical exertion using the Borg Rating of Perceived Exertion (BORG) scale. Additionally they commented on sites of discomfort, perceptions of force, and loss of range of motion. The root mean square and integrated sEMG value was significantly reduced at the LES and TES. Heart rate variability output variables did not show any significant difference. The BORG-Scale showed no difference, with a mean score of 2.5. The HAL decreased the magnitude and onset of muscle activity and force in the lower back in a repetitive lifting task. Reduction of the muscle force and activity required during the lifting process is meaningful regarding lower back pain prevention, and the HAL may contribute to reducing the incidence of lower back pain in the working population.

Exploring the Concept of Iso-perceptual Manifold (IPM): A Study of Finger Force-Matching Tasks

We used force-matching tasks between the two hands to test predictions of the recently introduced scheme of perception based on the concept of iso-perceptual manifold (IPM) in the combined afferent–efferent space of neural signals. The main hypothesis was that accuracy and variability of individual finger force matching would be worse in a four-finger task compared to one-finger tasks. The subjects produced accurate force levels under visual feedback by pressing with either all four fingers or by one of the fingers of a hand (task-hand). They tried to match the total four-finger force or individual finger forces by pressing with the other hand (match-hand, no visual feedback). The match-hand consistently overshot the task-hand force during single-finger matching episodes. It showed higher inter-trial force variability during single-finger matching when the task-hand performed the four-finger task compared to trials when the task-hand performed single-finger tasks. These findings confirm our main hypothesis by showing that perception of individual finger forces can vary in multi-finger tasks within a space (IPM) corresponding to veridical perception of total force. Matching hypothetical commands to fingers, rather than finger forces, could be responsible for the consistent force overshoots. Indices of inter-trial variance affecting and unaffecting total force showed strong stabilization of total force in the task-hand but not in the match-hand in support of an earlier hypothesis on the importance of visual feedback for force stabilization. No differences were seen between the right and left hands suggesting that the dynamic dominance hypothesis may not be generalizable to perceptual phenomena.

Modern test benches for dynamic tests of tractor tires

For testing tractor tires and their wear, special laboratory stands with imitation of real tire operating conditions are used. They provide the definition of such characteristics of the tire as the possibility of continuous movement at maximum speed, the perception of forces during curvilinear movement, dynamic radius, tire rolling resistance, degree of tire heating, etc. Such test benches allow to evaluate the reliability of the tires and to identify the possibility of increasing their life cycle. The most common test benches include a fixed platform, a running drum, hydraulic cylinders, clamping devices, an electric drum drive, tire rotation mechanisms, a personal computer and a control panel. One of the drawbacks of such test benches is the presence of high losses to overcome efforts in the mechanisms of rotation of tires. Therefore, the urgent issue is to find solutions to improve energy efficiency and reliability of tractor tire tests. The article analyzes test benches of foreign and domestic manufacturers for dynamic tire tests. Their technical characteristics, functional indicators and overall dimensions are considered. Considerable attention is paid to the shortcomings of each of the test benches. A modernized version of the test bench is proposed, in which the disadvantages of analogues are taken into account and eliminated. The design of such a test bench allows testing tires, simulating their interaction with an uneven road surface, as well as reducing energy consumption and increasing the reliability of tire tests. A kinematic diagram of the test bench and a functional diagram of the power part of the electric drive of the test bench are proposed. Based on the technical data of the test benches and their capabilities, a comparative table is given, as well as conclusions about the feasibility of using more energy-efficient drives for such test benches is proven.

Miniaturised optical fibre based palpations instrument for minimally invasive surgery

The lack of tactile and force perception during robot-assisted surgeries could lead to application of inadvertent forces resulting in tissue trauma and accidental tissue damage. In order to perform surgical procedures within tight spaces surrounded by sensitive soft tissues, surgeon’s ability to manoeuvre instruments with precision and control must be enhanced. Further, the tools with built-in tactile and force sensors enable surgeons to investigate surrounding tissues to determine surgical margins for dissection. This paper proposes a novel optical fibre based tactile probe capable of modelling tool tissue interactions to estimate tissue abnormalities. Tissue stiffness is estimated through an indentation technique. The proposed method allows rapid acquisition of tactile data as the instrument rolls over tissue surface in a near frictionless manner. The probe can concurrently measure both indentation force and indentation depth, which can be combined to develop a pseudo-colour stiffness image of the investigated tissue with abnormal regions clearly highlighted.

Dexterous Prosthetic Hand with Force Perception and Electrical Stimulation

Dexterous Prosthetic Hand with Force Perception and Electrical Stimulation

К ИСПЫТАНИЮ ВЕРТИКАЛЬНЫХ СВАРНЫХ СТЫКОВЫХ СОЕДИНЕНИЙ ПАНЕЛЬНЫХ ЗДАНИЙ

In this work, an experimental study of the welded concreted joint on the shear force was carried out. The test was carried out only for shear, since the main static purpose of vertical butt joints of panels is to ensure the perception of shear forces arising in the joints when the mating walls work together. The object of the study was a fragment of wall vertical connection 125 a series of large-panel residential buildings, the thickness of which was 160 mm and the total height is 550mm. In result of experimental research defined stress-strain state of vertical butt joints and proposed approximating the dependence of the deformation of the weld joint from shear forces. The test results can be used in the calculation of load-bearing systems of largt-panel buildings taking into account the nonlinear compliance of welded joints.

Cellular machinery for sensing mechanical force

For mechanical force to induce changes in cellular behaviors, two main processes are inevitable; perception of the force and response to it. Perception of mechanical force by cells, or mechanosensing, requires mechanical force-induced conformational changes in mechanosensors. For this, at least one end of the mechanosensors should be anchored to relatively fixed structures, such as extracellular matrices or the cytoskeletons, while the other end should be pulled along the direction of the mechanical force. Alternatively, mechanosensors may be positioned in lipid bilayers, so that conformational changes in the embedded sensors can be induced by mechanical force-driven tension in the lipid bilayer. Responses to mechanical force by cells, or mechanotransduction, require translation of such mechanical force-induced conformational changes into biochemical signaling. For this, protein-protein interactions or enzymatic activities of mechanosensors should be modulated in response to force-induced structural changes. In the last decade, several molecules that met the required criteria of mechanosensors have been identified and proven to directly sense mechanical force. The present review introduces examples of such mechanosensors and summarizes their mechanisms of action.

Improved force JND in immersive virtual reality needle insertion simulation

Haptic feedback in immersive virtual reality (IVR) systems is critical to enable a more intuitive and natural way of interacting with virtual objects. IVR-based haptic medical simulations such as needle insertion procedures have the potential to enhance clinicians’ haptic expertise. This work is a preliminary study on the use and implementation of IVR for needle simulators. Although few studies have quantified haptic skills such as force Just Noticeable Difference (JND) with the single finger, none have measured the force JND as recommended in the standard needle insertion protocol in an IVR environment. The hypothesis of this study is that there will be an improvement of force perception in the IVR, compared to that of the non-immersive virtual reality (NIVR) which facilitates the use of IVR for medical simulations. This paper emphasized on two objectives: firstly, the development of the observer state model for both the IVR and NIVR and the theoretical analysis of the psychophysical measures in both of the environments. Secondly, measures of force JND with the three fingers and comparison of these measures in NIVR to that of the IVR using psychophysical study with the force matching task, constant stimuli method, and isometric force probing stimuli to validate the model. Twenty voluntary subjects performed the experiment in both of the environments. Mean force JND and standard deviation of the JND were found to be 9.12% and 3.75% in the NIVR and 5.91% and 3.65% in the IVR (p value < 0.0001) which are in the same range of JNDs found in the literature (5–10%) for the NIVR using a single finger. Surprisingly, the results showed a better force JND in the IVR compared to that of the NIVR. Also, a simple state observer model was proposed to explain the improvement of force JND in the IVR. This study would quantitatively reinforce the use of IVR for the design of various medical simulators.

Occlusal force predicts global motion coherence threshold in adolescent boys

BackgroundBeneficial effects of mastication on cognitive abilities in the elderly have been shown in human studies. However, little is currently known about the effect of masticatory stimulation on cognitive and perceptual ability in younger populations. The purpose of the present study is to investigate the influences of masticatory stimulation on perceptual ability in adolescent boys.MethodsThe present study examined the relationship between occlusal force (i.e., masticatory stimulation) and visual perception ability in adolescent boys. Visual perception ability was quantified by measuring global motion coherence threshold using psychophysical method. As an index of masticatory stimulation, occlusal force was measured by pressure sensitive film. We also measured participants’ athletic ability, e.g. aerobic capacity and grip strength, as potential confounding factor.ResultsThe multiple regression analysis revealed a significant negative correlation between global motion coherence threshold and occlusal force, which persisted after controlling for confounding factors such as age and aerobic capacity.ConclusionsThis finding indicates that masticatory stimulation enhances visual perception in adolescent boys, indicating the possibility that beneficial effects of masticatory stimulation are observed not only in the elderly but in developing population consistently with the findings of the previous animal studies.

Design, Analysis and Experiment of a Tactile Force Sensor for Underwater Dexterous Hand Intelligent Grasping.

This paper proposes a novel underwater dexterous hand structure whose fingertip is equipped with underwater tactile force sensor (UTFS) array to realize the grasping sample location determination and force perception. The measurement structure, theoretical analysis, prototype development and experimental verification of the UTFS are purposefully studied in order to achieve accurate measurement under huge water pressure influence. The UTFS is designed as capsule shape type with differential pressure structure, and the external water pressure signal is separately transmitted to the silicon cup bottom which is considered to be an elastomer with four strain elements distribution through the upper and lower flexible contacts and the silicone oil filled in the upper and lower cavities of UTFS. The external tactile force information can be obtained by the vector superposition between the upper and lower of silicon cup bottom to counteract the water pressure influence. The analytical solution of deformation and stress of the bottom of the square silicon cup bottom is analyzed with the use of elasticity and shell theory, and compared with the Finite Element Analysis results, which provides theoretical support for the distribution design of four strain elements at the bottom of the silicon cup. At last, the UTFS zero drift experiment without force applying under different water depths, the output of the standard force applying under different water depth and the test of the standard force applying under conditions of different 0 C–30 C temperature with 0.1 m water depth are carried out to verify the performance of the sensor. The experiments show that the UTFS has a high linearity and sensitivity, and which has a regular zero drift and temperature drift which can be eliminated by calibration algorithm.

Feeling the force: how pollen tubes deal with obstacles.

Physical forces are involved in the regulation of plant development and morphogenesis by translating mechanical stress into the modification of physiological processes, which, in turn, can affect cellular growth. Pollen tubes respond rapidly to external stimuli and provide an ideal system to study the effect of mechanical cues at the single-cell level. Here, pollen tubes were exposed to mechanical stress while monitoring the reconfiguration of their growth and recording the generated forces in real-time. We combined a lab-on-a-chip device with a microelectromechanical systems (MEMS)-based capacitive force sensor to mimic and quantify the forces that are involved in pollen tube navigation upon confronting mechanical obstacles. Several stages of obstacle avoidance were identified, including force perception, growth adjustment and penetration. We have experimentally determined the perceptive force threshold, which is the force threshold at which the pollen tube reacts to an obstacle, for Lilium longiflorum and Arabidopsis thaliana. In addition, the method we developed provides a way to calculate turgor pressure based on force and optical data. Pollen tubes sense physical barriers and actively adjust their growth behavior to overcome them. Furthermore, our system offers an ideal platform to investigate intracellular activity during force perception and growth adaption in tip growing cells.

Simplifying Telerobotics: Wearability and Teleimpedance Improves Human-Robot Interactions in Teleoperation

In recent years, wearability has become a new fundamental requirement for an effective and lightweight design of human-robot interfaces. Among the different application fields, robotic teleoperation represents the ideal scenario that can largely benefit from wearability to reduce constraints to the human workspace (acting as a master) and enable an intuitive and simplified information exchange within the teleoperator system. This effective simplification is particularly important if we consider the interaction with synergy-inspired robotic devices, i.e., those that are endowed with a reduced number of control inputs and sensors, with the goal of simplifying control and communication among humans and robots. In this article, we present an integrated approach for augmented teleoperation where wearable hand/arm pose undersensing and haptic feedback devices are combined with teleimpedance (TI) techniques for the simplified yet effective position and stiffness control of a synergy-inspired robotic manipulator in real time. The slave robot consists of a KUKA lightweight robotic arm equipped with the Pisa/IIT SoftHand, both controlled in impedance to perform a drilling task-an illustrative example of a dynamic task with environmental constraints. The experimental results from ten healthy subjects suggest that the proposed integrated interface enables the master to appropriately regulate the stiffness and pose of the robotic hand-arm system through the perception of interaction forces and vision, contributing to successful and intuitive executions of the remote task. The achieved performance is presented in comparison to the reduced versions of the integrated system, in which either TI control or wearable feedback is excluded.

Research to Assembly Scheme for Satellite Deck Based on Robot Flexibility Control Principle

Deck assembly is critical quality control point in final satellite assembly process, and cable extrusion and structure collision problems in assembly process will affect development quality and progress of satellite directly. Aimed at problems existing in deck assembly process, assembly project scheme for satellite deck based on robot flexibility control principle is proposed in this paper. Scheme is introduced firstly; secondly, key technologies on end force perception and flexible docking control in the scheme are studied; then, implementation process of assembly scheme for satellite deck is described in detail; finally, actual application case of assembly scheme is given. Result shows that compared with traditional assembly scheme, assembly scheme for satellite deck based on robot flexibility control principle has obvious advantages in work efficiency, reliability and universality aspects etc.

Force sharing and other collaborative strategies in a dyadic force perception task.

When several persons perform a physical task jointly, such as transporting an object together, the interaction force that each person experiences is the sum of the forces applied by all other persons on the same object. Therefore, there is a fundamental ambiguity about the origin of the force that each person experiences. This study investigated the ability of a dyad (two persons) to identify the direction of a small force produced by a haptic device and applied to a jointly held object. In this particular task, the dyad might split the force produced by the haptic device (the external force) in an infinite number of ways, depending on how the two partners interacted physically. A major objective of this study was to understand how the two partners coordinated their action to perceive the direction of the third force that was applied to the jointly held object. This study included a condition where each participant responded independently and another one where the two participants had to agree upon a single negotiated response. The results showed a broad range of behaviors. In general, the external force was not split in a way that would maximize the joint performance. In fact, the external force was often split very unequally, leaving one person without information about the external force. However, the performance was better than expected in this case, which led to the discovery of an unanticipated strategy whereby the person who took all the force transmitted this information to the partner by moving the jointly held object. When the dyad could negotiate the response, we found that the participant with less force information tended to switch his or her response more often.

Muscle spindle thixotropy affects force perception through afferent-induced facilitation of the motor pathways as revealed by the Kohnstamm effect.

This study was designed to explore the effects of intrafusal thixotropy, a property affecting muscle spindle sensitivity, on the sense of force. For this purpose, psychophysical measurements of force perception were performed using an isometric force matching paradigm of elbow flexors consisting of matching different force magnitudes (5, 10 and 20% of subjects' maximal voluntary force). We investigated participants' capacity to match these forces after their indicator arm had undergone voluntary isometric conditioning contractions known to alter spindle thixotropy, i.e., contractions performed at long ('hold long') or short muscle lengths ('hold short'). In parallel, their reference arm was conditioned at the intermediate muscle length ('hold-test') at which the matchings were performed. The thixotropy hypothesis predicts that estimation errors should only be observed at low force levels (up to 10% of the maximal voluntary force) with overestimation of the forces produced following 'hold short' conditioning and underestimation following 'hold long' conditioning. We found the complete opposite, especially following 'hold-short' conditioning where subjects underestimated the force they generated with similar relative error magnitudes across force levels. In a second experiment, we tested the hypothesis that estimation errors depended on the degree of afferent-induced facilitation using the Kohnstamm phenomenon as a probe of motor pathway excitability. Because the stronger post-effects were observed following 'hold-short' conditioning, it appears that the conditioning-induced excitation of spindle afferents leads to force misjudgments by introducing a decoupling between the central effort and the cortical motor outputs.