A Review of Non-Invasive Haptic Feedback stimulation Techniques for Upper Extremity Prostheses <s> Electro Feedback Display <s> This paper reports a pilot study to explore the plausibility of using the phenomenon of phantom finger perception (PFP) in amputees to develop sensory feedback for prosthetic hand. PFP can be aroused by touching a specific part of the skin in the stump area of amputees. We hypothesized that transcutaneous electrical stimulation (TES) can evoke the similar PFP in amputees with electrodes placed at the same skin area. We tested this hypothesis in subjects with distal amputation at the forearm above the wrist. The areas of PFP on the stump skin of amputee subjects were first identified and labeled by manually touching the skin. Electrical stimulation was then applied to the same area with surface electrode. The subjects reported that the corresponding finger was touched with electrical stimulation, and gradation of sensation with increased strength of stimulation current was perceived in a similar way as reported in normal subjects. Peripheral nerve sprouting into the receptors in stump skin after amputation is speculated as the neural mechanism of PFP. Preliminary results support the hypothesis that PFP evoked by TES can be utilized to establish a direct sensory feedback from the fingers of prosthetic hand to the amputee. <s> BIB001 </s> A Review of Non-Invasive Haptic Feedback stimulation Techniques for Upper Extremity Prostheses <s> Electro Feedback Display <s> This research is motivated by the need of integrating cutaneous sensing into a prosthetic device, enabling a bidirectional communication between the amputee and the prosthetic limb. An electronic skin based on piezoelectric polymer sensors transduces mechanical contact into electrical response which is conveyed to the human subject by electrotactile stimulation. Rectangular electrode arrays are placed on each patient's forearm and experiments are conducted on five different subjects to determine how well the orientation, position and direction of single lines are recognized. Overall, subjects discriminate the different touch modalities with acceptable success rates. In particular, the direction is identified at best and longitudinal lines on the patient's skin are recognized with the highest success rates. These preliminary results assess the feasibility of the artificial skin - electrostimulation system for prosthetic applications. <s> BIB002 </s> A Review of Non-Invasive Haptic Feedback stimulation Techniques for Upper Extremity Prostheses <s> Electro Feedback Display <s> Tactile or touch sensing can enable an object's surface texture and other properties to be perceived which can facilitate grasping and manipulating various objects. Prosthetic hand users and operators of tele-operated robot arms also need to perceive these tactile properties by some means to effectively manipulate objects and performed skilled work. This paper introduces a tactile sensing and feedback system that is based on detecting surface vibrations in an artificial finger, when contact or friction with a surface is made, and appropriately stimulating nerves in the user's skin with electro-tactile feedback. This feedback system has benefits over existing systems because it can deliver a wide variety of sensations to the user and is compact, non-mechanical, wireless and comfortable for the user to wear. Experimental results are provided which show the potential of our system at achieving remote tactile sensing and feedback of textured surfaces. <s> BIB003 </s> A Review of Non-Invasive Haptic Feedback stimulation Techniques for Upper Extremity Prostheses <s> Electro Feedback Display <s> The lack of reliable sensory feedback has been one of the barriers in prosthetic hand development. Restoring sensory function from prosthetic hand to amputee remains a great challenge to neural engineering. In this paper, we present the development of a sensory feedback system based on the phenomenon of evoked tactile sensation (ETS) at the stump skin of residual limb induced by transcutaneous electrical nerve stimulation (TENS). The system could map a dynamic pattern of stimuli to an electrode placed on the corresponding projected finger areas on the stump skin. A pressure transducer placed at the tip of prosthetic fingers was used to sense contact pressure, and a high performance DSP processor sampled pressure signals, and calculated the amplitude of feedback stimulation in real-time. Biphasic and charge-balanced current pulses with amplitude modulation generated by a multi-channel laboratory stimulator were delivered to activate sensory nerves beneath the skin. We tested this sensory feedback system in amputee subjects. Preliminary results showed that the subjects could perceive different levels of pressure at the tip of prosthetic finger through evoked tactile sensation (ETS) with distinct grades and modalities. We demonstrated the feasibility to restore the perceptual sensation from prosthetic fingers to amputee based on the phenomenon of evoked tactile sensation (ETS) with TENS. <s> BIB004 </s> A Review of Non-Invasive Haptic Feedback stimulation Techniques for Upper Extremity Prostheses <s> Electro Feedback Display <s> This paper presents the development of a myoelectric prosthetic hand based on a 3D printed model. A myoelectric control strategy based on artificial neural networks is implemented on a microcontroller for online position estimation. Position estimation performance achieves a correlation index of 0.78. Also a study involving transcutaneous electrical stimulation was performed to provide tactile feedback. A series of stimulations with controlled parameters were tested on five able-body subjects. A single channel stimulator was used, positioning the electrodes 8 cm on the wrist over the ulnar and median nerve. Controlling stimulation parameters such as intensity, frequency and pulse width, the subjects were capable of distinguishing different sensations over the palm of the hand. Three main sensations where achieved: tickling, pressure and pain. Tickling and pressure were discretized into low, moderate and high according to the magnitude of the feeling. The parameters at which each sensation was obtained are further discussed in this paper. <s> BIB005 </s> A Review of Non-Invasive Haptic Feedback stimulation Techniques for Upper Extremity Prostheses <s> Electro Feedback Display <s> Myoelectric prostheses are successfully controlled using muscle electrical activity, thereby restoring lost motor functions. However, the somatosensory feedback from the prosthesis to the user is still missing. The sensory substitution methods described in the literature comprise mostly simple position and force sensors combined with discrete stimulation units. The present study describes a novel system for sophisticated electrotactile feedback integrating advanced distributed sensing (electronic skin) and stimulation (matrix electrodes). The system was tested in eight healthy subjects who were asked to recognize the shape, trajectory, and direction of a set of dynamic movement patterns (single lines, geometrical objects, letters) presented on the electronic skin. The experiments demonstrated that the system successfully translated the mechanical interaction into the moving electrotactile profiles, which the subjects could recognize with a good performance (shape recognition: $86\pm 8\%$ lines, $73\pm 13\%$ geometries, $72\pm 12\%$ letters). In particular, the subjects could identify the movement direction with a high confidence. These results are in accordance with previous studies investigating the recognition of moving stimuli in human subjects. This is an important development towards closed-loop prostheses providing comprehensive and sophisticated tactile feedback to the user, facilitating the control and the embodiment of the artificial device into the user body scheme. <s> BIB006 </s> A Review of Non-Invasive Haptic Feedback stimulation Techniques for Upper Extremity Prostheses <s> Electro Feedback Display <s> Human motor control relies on a combination of feedback and feedforward strategies. The aim of this study was to longitudinally investigate artificial somatosensory feedback and feedforward control in the context of grasping with myoelectric prosthesis. Nine amputee subjects performed routine grasping trials, with the aim to produce four levels of force during four blocks of 60 trials across five days. The electrotactile force feedback was provided in the second and third block using multipad electrode and spatial coding. The first baseline and last validation block (open-loop control) evaluated the effects of long- (across sessions) and short-term (within session) learning, respectively. The outcome measures were the absolute error between the generated and target force, and the number of force saturations. The results demonstrated that the electrotactile feedback improved the performance both within and across sessions. In the validation block, the performance did not significantly decrease and the quality of open-loop control (baseline) improved across days, converging to the performance characterizing closed-loop control. This paper provides important insights into the feedback and feedforward processes in prosthesis control, contributing to the better understanding of the role and design of feedback in prosthetic systems. <s> BIB007 </s> A Review of Non-Invasive Haptic Feedback stimulation Techniques for Upper Extremity Prostheses <s> Electro Feedback Display <s> Purpose ::: ::: ::: ::: ::: The purpose of this study is to present a novel hybrid closed-loop control method together with its performance validation for the dexterous prosthetic hand. ::: ::: ::: ::: ::: Design/methodology/approach ::: ::: ::: ::: ::: The hybrid closed-loop control is composed of a high-level closed-loop control with the user in the closed loop and a low-level closed-loop control for the direct robot motion control. The authors construct the high-level control loop by using electromyography (EMG)-based human motion intent decoding and electrical stimulation (ES)-based sensory feedback. The human motion intent is decoded by a finite state machine, which can achieve both the patterned motion control and the proportional force control. The sensory feedback is in the form of transcutaneous electrical nerve stimulation (TENS) with spatial-frequency modulation. To suppress the TENS interfering noise, the authors propose biphasic TENS to concentrate the stimulation current and the variable step-size least mean square adaptive filter to cancel the noise. Eight subjects participated in the validation experiments, including pattern selection and egg grasping tasks, to investigate the feasibility of the hybrid closed-loop control in clinical use. ::: ::: ::: ::: ::: Findings ::: ::: ::: ::: ::: The proposed noise cancellation method largely reduces the ES noise artifacts in the EMG electrodes by 18.5 dB on average. Compared with the open-loop control, the proposed hybrid closed-loop control method significantly improves both the pattern selection efficiency and the egg grasping success rate, both in blind operating scenarios (improved by 1.86 s, p < 0.001, and 63.7 per cent, p < 0.001) or in common operating scenarios (improved by 0.49 s, p = 0.008, and 41.3 per cent, p < 0.001). ::: ::: ::: ::: ::: Practical implications ::: ::: ::: ::: ::: The proposed hybrid closed-loop control method can be implemented on a prosthetic hand to improve the operation efficiency and accuracy for fragile objects such as eggs. ::: ::: ::: ::: ::: Originality/value ::: ::: ::: ::: ::: The primary contribution is the proposal of the hybrid closed-loop control, the spatial-frequency modulation method for the sensory feedback and the noise cancellation method for the integrating of the myoelectric control and the ES-based sensory feedback. <s> BIB008
The electro feedback display is the haptic method of delivering low-level electrical current pulses to the user's skin in order to depolarize skin afferents, thereby eliciting the haptic sensation BIB006 . The electro feedback stimulators are usually formed from a single row of activating electrode pads BIB007  [83] or from matrix patterns BIB006 BIB002 . This is due to the distribution of the electrode pads is completely depending on the design of the haptic system and the nature of the measured signal of the sensory system. Table 5 presents a short survey of the studies in electro feedback display. The ability of the electro haptic feedback stimulation system to help the amputees to detect the contact pressure and the surface texture at the same operation time was investigated in BIB003 . For this reason, a lightweight vibration sensor was attached to the artificial sensor in order to sense the texture of the plastic, sand, rice, and matchsticks surfaces. Different surfaces were arranged over a textured rotatable platter and the artificial finger was allowed to slide freely over it. During the experiment, the main function of the electro feedback stimulator is to provide a wide range of frequencies to the users about the contact pressure and the surface texture in a way that the tactile information can be clearly distinguished by the users. The evaluation tests showed that all the engaged volunteers were able to detect the contact pressure successfully without brain confusion. The volunteers recorded around 75% average discrimination accuracy at the surface texture detection tests. The feasibility of recovering the touch sensation from prosthetic fingertip based on the evoked tactile sensation (ETS) was demonstrated in BIB001 BIB004 . The transcutaneous electrical nerve stimulation (TENS) electro feedback system was used to stimulate patient's skin and convey the tactile information to his brain. In addition, the functionality of the electro stimulators to relocate the sensation of the tickling, contact pressure, and pain during touching and grasping objects was investigated BIB005 . The experimental setup was divided into two main loops: feed-forward, and feed-backward loops, as shown in Fig. 8 . Controlling the movement and the performance of the 3D prosthetic hand model prosthetic hand by using EMG signals are the feed-forward loop. The feed-backward loop represents the haptic feedback stimulation system, in which the contact pressure at the prosthetic hand is measured by the pressure sensors and restored to the user by two electro displays attached at the user's forearm. The results validated the efficacy of the electro feedback stimulators to convey the tactile information in a quick manner. Furthermore, the effectiveness of the suggested hybrid closed-loop controller that integrated with the upper limb prostheses to enhance the operation efficiency and accuracy for crisp objects has been shown BIB008 . 