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For the kilometer-level electromagnetic launch system, a high-speed double-sided linear permanent magnet (PM) linear motor is presented in this paper. To enhance the average thrust force, reduce the thrust ripple and normal force of linear motor, a segmented trapezoidal PM shaping method is proposed. Compared with conventional PM shaping method, the segmented trapezoidal PMs achieves less force ripple, greater average force and lower manufacturing difficulty. The risk of PM demagnetization fault has been taken into account. To reduce the losses in the mover of the linear motor, a non-metallic light-weight mover structure is proposed. The effectiveness of segmented trapezoidal PMs and non-metallic light-weight mover are verified by the finite element method and experiment.

This paper introduces a wheel-based vertical propagation robot, $Ibex$ , for visual inspection of both flat and curved surfaces. The platform is modular, consisting of vacuum-based adhesion modules and steerable-wheel locomotion modules. The adhesion module consists of a unconventional design of suction cup with sufficient structural flexibility and single-axis translation freedom that helps with adhesion to flat and curved vertical surfaces. Through experiments, we validate the locomotion, adhesion, and conformation mechanisms of the robot, and collated data of the adhesion module such as differential pressure as well as normal force measurements using force sensitive resistors and a thrust force meter. We show that the platform has ability to generate a considerable amount of adhesion force while demonstrating the ability to adhere to and move on variables types of surfaces as well as various surface curvatures including plastered cement pillars and aircraft skins.

Three-dimensional tactile sensing in smart devices is witnessing an increasing demand. In this study, a three-dimensional tactile sensor is proposed according to the principle of triboelectricity by using polydimethylsiloxane (PDMS) and polyethylene oxide (PEO) films. Use of PDMS-ZnO composite films increases the output voltage of the electrodes. The sensor is designed with a cross beam-shaped pressure head to enable sensing normal forces in five directions. The working mechanism of the sensor is analyzed using the finite element method. The calculation results indicate a linear relationship between the output voltage and the force. The simulation results also demonstrate that the output voltage is linearly correlated with the applied force in the range of 1–30 N. Test results show that the sensor can sense the magnitude, frequency, and direction of the force as well as measure the duration of the force. The hardness of the object has a significant effect on the output voltage. Finally, the sensor is tested on a manipulator grasping an object to demonstrate its ability to sense the contact and sliding of the object.

Permanent magnet linear synchronous motors have the advantages of high thrust density, high acceleration, high speed, and high efficiency, which are widely used in CNC lathes, lithography machines, rail transportation, etc. In high-speed, high-precision servo control systems, detent force fluctuation caused by end effect can easily cause problems such as speed fluctuation, mechanical vibration and electromagnetic noise, which affect the servo performance of permanent magnet linear synchronous motors. Aiming at the detent force fluctuation caused by the end effect of permanent magnet linear synchronous motor, this paper proposes a stepped double auxiliary pole method. The method has a good suppression effect on the end normal force fluctuation and the end thrust fluctuation, which improves the servo performance of the permanent magnet linear synchronous motor in the high-precision servo system. In the traditional methods of suppressing the fluctuation of end detent force, two common methods are using a magnetic isolation aluminum plate and optimizing the auxiliary pole size. The former needs a magnetic isolation aluminum plate to connect the auxiliary pole and the primary mover. Therefore, it needs to add the connection device to connect those three parts. The connection device complicates the auxiliary pole part and increases manufacturing difficulty. The latter does not change the manufacturing process, but in the early design process, the optimum size of the auxiliary needs to be considered. Compared with these two methods, the one proposed in this paper avoids the complex structure of magnetic isolation aluminum plate, the stepped double auxiliary pole is integrated with the primary mover. Moreover, it has a fixed structure with optimum size. Therefore, the method in the paper does not change the manufacturing process, improves the strength of the initial pole structure, and reduces design period. Finally, the finite element analysis by ANSYS was performed to illustrate the correctness and effectiveness of the method.

This paper shows the influence of the air-gap length variations in a low speed linear induction motor behavior. Changes in the air-gap length produces variations in the equivalent circuit model parameters of the low speed linear induction motor, altering the mechanical characteristics of the motor. This analysis is extended to the dynamic model of the linear induction motor. A new dynamic model is proposed to take into account the air-gap variations and an expression to calculate the dynamic normal force developed by the motor is presented. The proposed models are compared to the static and dynamic computational simulations using the finite element method. The results show the proposed model has a good correspondence with the computational simulations.

The paper presents a mechanical design for a haptic hand exoskeleton that can be employed in delivering sensation to a fingertip of an operator while he interacts with virtual objects in the computer simulation. The linkage structure of the device is designed according to the skeletal characteristics of a human finger, which allows it to create the normal force on the fingertip while natural movements of fingers are maintained. Moreover, motion range of the designed hand exoskeleton is carefully calculated to guarantee full capacity of human fingers. Evaluation of the design, where its kinematic structure and force transmission were analysed, shows effectiveness of the proposed device.

Intelligent power grasp of robotic gripper system has been instrumental in metal-working industries as well as handling of nuclear material in recent past. Slip-resistant, robust gripping of disc-shaped material during remote manipulation is a challenge in material handling. In a nuclear fuel manufacturing lab, sensitive fuel materials (objects) are handled in the form of a disc (melt) that is pre-cast. Depending on the process treatment, the metal discs are categorized as delicate, hard or soft. The metal discs that were handled by the robotic system and used in the experiment have a diameter of 60mm, a thickness of 15mm, and a weight of 2.3 kg., It is crucial to take care of the paradigms like grip force, profile and perception of slide for job planning and management of a robot in a hazardous radioactive environment. A multi-sensory tactile array is designed indigenously and fabricated by utilising commercial sensors attached to the prototype gripper so as to make it an intelligent instrumented-jaw gripper. The custom-built tactile sensory system is made up of a) force sensing resistors (FSRs) in a specific array, b) a matrix of FSR in the centre, c) PVDF (Polyvinylidene Fluoride) sensors in the perimeter and d) infrared (IR) sensors placed in a predetermined architecture. The mounting of the customized gripper sensory system includes a 3x2-array of FSRs and other sensors, each having a spatial resolution of 5 mm and a sensing area of $15,000 mm^{2}$. While PVDF sensor is employed for dynamic contact point estimation, texture recognition is accomplished using high frequency response. An integrated form of proximity and ambient light sensor is utilised (mimicing distance sensor) to detect the presence of an object and improve gripper alignment during grasping. This sensor-instrumented processing was achieved through microcontroller-based programming and allied electronics, such as scanning the array & storing the data. LabView® was used to record the digital signals and analysis of time-spanned raw data. Calibration was carried out to ensure that the acquired data was repeatable and reliable. The paradigms of indigenous development of the integrated sensory system for the gripper as well as its calibration, dynamic features and response characteristics are discussed in this paper. The tactile matrix has a force range of 30N, a resolution of 0.3N and a sensitivity of 0.5V/N., The FSR sensors produced a nonlinear relationship at various force ranges and the hysteresis therein was found to vary with load range and frequency. At lower frequencies of 0.2 and 0.8 Hz, cycle drift was significant, with a maximum inaccuracy in force value of 0.5 N. The force measuring inaccuracy of normal force was less than 5% at sensitive places. Based on the repeated experimentation, the developed matrix sensor was entrusted to have nearly 95% accuracy rate in recognising different textures. The developed tactile sensor matrix was found to be robust and it has good reproducibility in parameters like contact force measurement, contact point estimate, slip detection and texture recognition, according to the experimental results. To not withstanding benefits the developed tactile sensor system was also comprehended with few on-job limitations, signaling run-time error conditions.

As touchscreens have become a standard feature in mobile devices, technologies for presenting tactile texture feedback on the panel have been attracting attention. We tested a new method for presenting natural materials using an electrostatic tactile texture display. In this method, the frictional forces are decomposed into low- and high-frequency components. The low-frequency component was modeled based on Coulomb’s friction law, such that the friction force was reactive to the finger’s normal force. The high-frequency component was modeled using an auto-regressive model to retain its features of frequency spectra. Four natural material types, representing leather, cork, denim, and drawing paper, were presented to six assessors using this method. In a condition where only the low-frequency friction force components were rendered, the materials were correctly recognized at 70%. In contrast, when the high-frequency components were superposed, this rate increased to 80%, although the difference was not statistically significant. Our approach to combine a physical friction model and frequency spectrum for low- and high-frequency components, respectively, allows people to recognize virtual natural materials rendered on touch panels.

This paper presents a novel flexible triaxial force sensor based on the capacitive pressure sensor array. The main structures of the sensor consist of the triangular pyramid microstructure electrode and the orthogonal triangular pyramid microstructure with the spacing of $20\ \mu\ \mathrm{m}$ , which makes the sensor have a large pressure detection range and high sensitivity at the same time. The triaxial force sensor based on the sensor array can measure the triaxial force in real time, and the ranges of normal force and tangential force are 0–3 N and 0–0.5 N, respectively. The proposed flexible triaxial force sensor is expected to have a good application prospect in the field of human-computer interaction.

This paper proposes a bioinspired spiny foot for wall-climbing robots. Inspired by the fluid-filled sac under the lamella in gecko's foot, a fluid-filled sac with soft membrane is designed to ensure that the contact force between spiny foot and the climbing surface are evenly distributed among all spines. Each spine has two degrees of freedom, and the tangential motion and normal motion of all spines are actuated by two fluid-filled sacs respectively. When the spiny foot tries to adhere on the rough surface, spines move along the surface to find a proper asperity and engage on it. Although the moving displacements of spines are different, the tangential forces as well as the normal forces acted on spines are almost the same due to the constant hydraulic pressure in sacs behind them. With this load-sharing capacity, the spiny foot's adhesion property is significantly improved, and it could be used in improving the climbing stability and load-capacity of climbing robots.

This paper presents an innovative continuously variable transmission for robots, which is classified as K-H-V type. The innovative CVT mainly includes sun pulley, planetary pulley, metal v-belt, eccentric input shaft and others. This simple and effective structure can effectively reduce manufacturing costs and improve motor efficiency. In addition, this paper also studies the continuous geometric model of the metal v-belt and analyzes the kinematics and dynamics of a single metal segment. Moreover, taking pulley as the research object, the factors affecting the stability of the v-belt transmission ratio are analyzed. Based on the above physical model, the dynamic simulation is carried out. The results show that changing trends of the tension and normal force are consistent with the classical chain mathematical model, which provides theoretical reference for robots motion control.

In order to solve the problem of large normal force of bilateral moving armature permanent magnet linear DC motor, Fourier expansion method was used to obtain the analytical expression of normal force on permanent magnet, considering the cogging effect. The research shows that the armature current can inhibit the normal force on the permanent magnet, but at the same time it increases the fluctuation of the normal force. The no-load normal force of the permanent magnet can be reduced by 440N by decreasing the pole arc coefficient and tooth width. Although part of the thrust performance is lost, the thrust of the linear motor can be compensated under the condition of higher current, and the thrust fluctuation is basically unchanged. The simulation results are basically consistent with the analytical results, which verifies the correctness of the analytical analysis method of normal force fluctuation.

A novel double-sided permanent magnet linear synchronous motor (PMLSM) is proposed in this paper, which forms a three-phase balanced structure by arranging a specific distance between the single phase-group concentrated-coil (PGCC) windings. First, the model of the double-sided PMLSM is established. Then, the air gap magnetic field and operating principle of the proposed motor are theoretically analyzed. Finally, based on the analysis of the air gap magnetic field, the cogging normal force of the proposed PMLSM is theoretically analyzed and verified by the finite element method (FEM).

In the suspended permanent magnet maglev train, the permanent magnet array is used as the suspension structure, and the short stator linear induction motor is used as the traction structure. The suspension system is a self-stabilizing system. As the vertical force changes, the suspension gap and the motor air gap are changing. The change in the air gap of the motor causes the output thrust to fail to meet the requirements; at the same time, the normal force of the system will also fluctuate. The normal force is the vertical disturbance of the bogie, which has a greater impact on the dynamic posture of the bogie and needs to be adjusted. control. In this paper, the secondary magnetic field orientation strategy is adopted, the end effect parameters are introduced, and the dynamic mathematical model of the linear induction motor is established. On this basis, a constant slip vector control system based on the secondary magnetic field orientation is built; The air gap between the secondary will produce dynamic changes, and a variable air gap model of the motor is built; at the same time, according to the actual operation of the train, thrust compensation is introduced. Based on the stable normal force and thrust of the original constant slip control system, the given thrust is compensated. Value so that the output thrust meets the requirements. The simulation experiment compares the proposed control strategy with the variable air gap constant slip frequency control strategy, which verifies the effectiveness of the method under typical operating conditions.

This paper investigates new methods for estimating the braking torque generated by carbon brakes mounted on MotoGP class motorcycles. The operating characteristics of the brake is determined by taking into account that the friction coefficient between the pads and the disc depends on three main factors: the disc temperature, the disc-pads relative speed and the normal force applied. Firstly, a numerical model based on an optimal estimation algorithm is implemented to represent the thermal dynamics of the system. In particular, the monitoring of the brake temperature is performed through a Bayesian recursive filtering algorithm, in which the information measured by one sensor is combined with a prediction made on the basis of a physical model. Then, since the exact physical relationship between the three inputs and the friction coefficient is very hard to find by using a classical model-based approach, an artificial neural network is developed to approximate the unknown underlying mapping function from inputs to output.

This paper describes an eddy current brake (ECB) device consisting of AC excitation and ferromagnetic railway. The braking force can be generated with non-contact and low noise caused by the reaction between the eddy current and excitation current. In this paper, the structure of the brake is introduced detailedly. In addition, the three-dimensional finite element analysis (FEA) model of ECB is established. Meanwhile, the experiment system of the rail ECB is built to study the braking characteristics. The validity of FEA simulation is verified by experimental results. It is found that with the increase of speed, the braking force increases linearly to a maximum value first, then slowly decreases, while the normal attractive force decreases continuously. The braking characteristic matches the requirements for the high-speed running trains which need large braking force and low normal force in the deceleration process, so it can be used as an auxiliary braking method in the high-speed railway.

The sling lift transfer system is commonly used in hospital and care home settings to transfer immobile and limited mobility patients from bed to chair or gurney. Even though this is the current standard of care, injuries to patients because of the forces applied to skin by the lift occur frequently. The lifts cause both normal and shear forces on the skin, and previous studies have only measured and reported on the applied normal forces with no assessment of shear. In this work, we use a novel shear and normal force sensor designed specifically to assess forces on skin and report the dynamic normal and shear forces during a sling lift. The shear forces are shown to be up to 8N for a partial lift of an adult male and occur both laterally and longitudinally along the thigh. Shear forces pull the skin and can cause injury, especially as skin tends to thin with age and become more susceptible to damage. This is the first reporting of shear forces during patient lifts.

This study proposes a novel design to implement a triaxial tactile force sensor, as shown in Fig. 1. The tactile force sensor is fabricated by TSMC standard CMOS process. The normal and shear forces sensing capabilities are achieved by three independent sensing components monolithically integrated on a single chip. Capacitive sensing membrane forms the normal force detection element and piezo-resistive bridges form the shear force detection elements. Merits of the design include (Fig. 2): (1) fully-clamped square-diaphragm array as the capacitive-type normal force sensing element: flexible only in out-of-plane direction (z-axis) to detect the normal load and avoid the cross-talk from shear forces; (2) clamped-clamped beam with Wheatstone bridge circuits as the piezo-resistive shear force sensing elements: flexible only in one in-plane direction (x-axis or y-axis) to detect the single axis share load, and the cross-talk from normal load is removed by the Wheatstone bridge circuits. Measurement results show the sensitivities of the proposed tri-axial tactile force sensor are 1.26 fF/N in z-axis, 2.043 mV/N in x-axis, 2.248 mV/N in y-axis and have less than 10% overall crosstalk.

This paper proposes a wide range 3 dimensional (3D) tactile sensor with variable sensitivity by using the robust bridge, array pyramid structure, and different Young's modulus and thickness of replaceable elastic layers on the assembled sensor's surface. In the structure of the sensor, the forces acting on the surface of the elastomer were transmitted to the bridges and silicon chip through the pyramids. Moreover, add one softer elastic layer on the surface of the PDMS cap, the hollow area will be compressed larger under the action of pressure since the hollow structure of the PDMS cap and different modulus between the elastic layer and PDMS cap. The sensitivities of this developed sensor increased three times compared to this sensor without an elastic layer in the measurement range of 100kPa (normal force).

The paper deals with an approach to reduce the detent force of double-sided flat linear permanent magnet synchronous machines (PMSMs). The study is initiated by a finite element analysis (FEA)-based investigation of the detent and normal forces of a conventional concept with aligned PM rows mounted on both mover sides. It is found that while it exhibits a quasi-null normal force, the concept is penalized by a huge detent force. An attempt to reduce such a drawback consisting in shifting the PM rows is proposed. Its effectiveness in reducing the detent force is demonstrated by FEA. However, it leads to a remarkable increase of the normal force. In order to minimize this latter, a second design approach consisting in a unilateral extension of both sides of the stator magnetic circuit, is proposed. It is shown that selecting 50% for both PM shift-to-the pole pitch and stator extension length facing the air gap-to-the pole pitch ratios yields acceptable peak-to-peak values of the detent and normal forces. The force production of the resulting machine is then evaluated and compared to the conventional concept one. In spite of the minimization of the force ripple, its mean value is limited to 50%. An approach consisting in a reconfiguration based on the star of slots of the armature in both stator sides, is proposed and assessed by FEA. As a result, an increase of the mean force as well as a reduction of the force ripple are gained.

This article introduces a novel double-sided linear hybrid excitation flux switching machine (DSLHEFSM) with yokeless secondary suitable for long stroke applications. The significant to this novel machine is the elimination of the secondary yoke, which can reduce the volume of the secondary. To reduce cost, ferrite magnets with reduced volume as compared to conventional design are utilized. In order to increase the thrust force density and reduce thrust force ripple under load conditions, the impact of some main design parameters, including split ratio, AC winding slot area, stator pole alignment, stator pole width, stator pole height and turn-on angle are investigated through finite element analysis. The electromagnetic performances of the LHEFSM are analysed including flux linkage, detent force, normal force, no-load EMF, force-velocity curve. Within the same volume constraint and electrical loading, the proposed model achieved higher average thrust force than the conventional model.

To achieve active compliance in the robot deburring process, a compliance control method of deburring robots based on force impedance is proposed. An impedance model between the reference deburring trajectory and contact force is constructed, based on the force feedback. The force impedance is integrated into the position control loop of robots in the Cartesian coordinates. On-line adjustment of the robot displacement and velocity is realized using normal force and tangential force, respectively. The control system simulation is carried out in the Simulink environment using the S-function. Results show that this method guarantees the displacement tracking performance of the robot, and achieves the displacement compliance through the normal force, as well as the velocity compliance through the tangential force.

A capacitive tactile sensor based on conventional four-planar-capacitor arrangement was advanced in electrode arrangement. The advanced design enhanced the spatial resolution of the tactile sensing unit without sacrificing its sensitivity because the sizes of the four capacitors were not altered. Results indicated that the spatial resolution was enhanced for more than doubled with normal force sensitivity of 3.261 pF/N and the average detection tolerance of the shear angle negligible. This work provided a solution to existing conventionally designs and existing capacitive tactile sensors to enhance the spatial resolution simply by algorithms instead of by any laborious physical modifications.

The ability to measure multi-axis contact forces and contact surface normals in real time is critical to allow robots to improve their dexterous manipulation and locomotion abilities. This paper presents a new fingertip sensor for 3axis contact force and contact location detection, as well as improvements on an existing footpad sensor through use of a new artificial neural network estimator. The fingertip sensor is intended for use in manipulation, while the footpad sensor is intended for high force use in locomotion. Both sensors consist of pressure sensing elements embedded within a rubber hemisphere, and utilize an artificial neural network to estimate the applied forces (f x , f y , and f z ), and contact angles (θ and φ) from the individual sensor element readings. The sensors are inherently robust, and the hemispherical shape allows for easy integration into point feet and fingertips. Both the fingertip and footpad sensors demonstrate the ability to track forces and angles accurately over the surface of the hemisphere (θ=±45° and φ=±45°) and can experience up to 25N and 450N normal force, respectively, without saturating. The performance of the sensor is demonstrated with experimental results of dynamic control of a robotic arm with real-time sensor feedback.

This contribution focuses on the analytical and finite element modelling of the thermo-mechanical behaviour of a friction-pendulum bearing device for passive seismic isolation. Influences of some crucial factors, such as the magnitude and the rate of change of the sliding velocity, the weight of the superstructure, and the rise in temperature on the force-displacement relationship characterizing the isolator, are studied. Numerical results obtained for a realistic testing protocol (plausible value of the applied normal force and sliding velocity) are presented.

In hospitals and care facilities, immobile patients are typically moved using methods such as the sling lift. This method is considered to be an acceptable risk for both the patient and health care workers involved in the transfer. However, it is known that the sling method increases the pressure on a patent’s skin due to a concentration of force, especially around the thigh and posterior regions, which can lead to contusions and other skin injuries. To solve this problem, Able Innovations Inc. is creating an alternative transfer technology that has the potential to reduce the pressure on the patient. In this work, we will assess the forces that are applied to the patient’s body by both the traditional sling transfer method and the new system. This work will evaluate a novel sensor used to measure the shear and normal force applied to the skin. A comparison of the forces applied to simulated skin (leather) and low friction tin-foil showed no difference indicating minimal shear forces are applied by system. Based on the results gathered, it was determined that the sensor used was able to reproduce previously reported results for the normal forces associated with sling lifts. It was found that the normal force concentration for the sling lift was approximately 2. 67KPa, whereas the new system only showed a normal force concentration of 700Pa. The latter is a 16% increase over the natural force due to normal body weight, whereas the comparable sling increase is over 300%.

Assistive grouser is an alternative grouser purposed by previous researchers that were used to help wheel rover to improve its performance especially when traversing on unconsolidated soft sand inclination slope. When using a normal grouser (conventional grouser), as the wheel rotates, the grouser pushes the sand particles under the wheel upward and toward the back of the wheel, and causing the wheel to get stuck into the sand surface as the wheel starts digging the sand. But by attaching the assistive grouser, it helps to minimize the subsequence sinkage. Assistive grousers are able to adjust its angle of attack when penetrating into the sand slope surface. Assistive grouser produces horizontal traction force that is similar to the bulldozing movement concept. When assistive grouser moves, it enters and exits sand surface without moving a large amount of sand particles from below of the wheel toward the back of the wheel and prevent the wheel from the stuck phase. From the previous experiment, by using assistive grouser with adjustable angle, it helps to improve the performance of wheel rover in term of minimizing the sand movement from under the wheel when the wheel rotates, less sinkage, and less current consumed during the movement of the wheel. However, during the experiment, the interaction between the assistive grouser and the sand cannot be seen clearly. The purpose of this study is to investigate and observe the interaction between assistive grouser (with varying angle of attack) and the sand particles especially on sand surface inclination slope by using computer simulation-Discrete Element Method (DEM) simulation at high slip condition. From the simulation, the effect of adjustable assistive grouser angle toward the traction force generated when the grouser and sand interact was observed. The highest normal force generated by using adjustable assistive grouser with 30-degree angle is around 900 N while the highest normal force generated by assistive grouser 0-degree angle is around 450 N. Assistive grouser that have same angle with the sand surface slope produced higher normal force and lead to produce higher traction force. The traction force helps the rover to climb the surface slope and move forward. And by using assistive grouser 30-degree, the area of destructive area is 230 cm2 which is bigger compared to assistive grouser 0-degree with 161 cm2. Destructive area portrays the relation between the grouser-sand and sand-sand particles.

In this study, the material of the dielectric layer was changed to reduce the structural rigidity of a capacitive tactile sensor, achieving the result of increasing the detection sensitivity without affecting the spatial resolution. Simulation and experimental results showed that the sensitivity of the sensor can be greatly improved by changing the elastomeric dielectric layer from a solid structure to a hollow structure. When the normal force was 0.25 N, the average detection sensitivity of the hollow structure was 32 pF/ N. Compared with the solid counterpart, the sensitivity was increased by roughly 600 times. When the shear force was 1.5 N, the average detection sensitivity of the hollow structure was 0.1 pF/N. Compared with the solid counterpart, it showed an improvement of at least five times regardless of the shear angle. In addition, the measured shear angle exhibited a tolerance of no more than 4°, which was similar to the announced sensors.

Ultrasonic wire bonding is a solid-state joining process, used in the electronics industry to form electrical connections, e.g. to connect electrical terminals within semiconductor modules. Many process parameters affect the bond strength, such like the bond normal force, ultrasonic power, wire material and bonding frequency. Today, process design, development, and optimization is most likely based on the knowledge of process engineers and is mainly performed by experimental testing. In this contribution, a newly developed simulation tool is presented, to reduce time and costs and efficiently determine optimized process parameter. Based on a co-simulation of MATLAB and ANSYS, the different physical phenomena of the wire bonding process are considered using finite element simulation for the complex plastic deformation of the wire and reduced order models for the transient dynamics of the transducer, wire, substrate and bond formation. The model parameters such as the coefficients of friction between bond tool and wire and between wire and substrate were determined for aluminium and copper wire in experiments with a test rig specially developed for the requirements of heavy wire bonding. To reduce simulation time, for the finite element simulation a restart analysis and high performance computing is utilized. Detailed analysis of the bond formation showed, that the normal pressure distribution in the contact between wire and substrate has high impact on bond formation and distribution of welded areas in the contact area.

Belt grinding is a commonly used finishing process that can reduce defects and burrs created by previous machining procedures. While it has been studied for a long time, researchers have mostly focused on methods that use grinding wheels, while other methods have seldom been addressed. Aiming to develop a force-sensorless grinding system, we propose a new 3-dimensional (3D) model that estimates the normal force being generated between workpieces and the grinding belt with a free strand of abrasive belt. The 3D model was constructed using integrated 2D interaction forces between the workpieces and the abrasive belt, and the latter force derived based on the tension force of the abrasive belt and the geometric contact configuration. A virtual simulator was developed and added to the geometric-based digital twin of the grinding system, forming a physics engine. The model was experimentally evaluated using spheres, cylinders, and frustums grinding specimens. The results confirm that the model can successfully predict normal forces.

The goal of achieving 'universal grasping' where many objects can be handled with minimal control input is the focus of much research due to potential high impact applications ranging from grocery packing to recycling. However, many of the grippers developed suffer from limited sensing capabilities which can prevent handing of both heavy bulky items and also lightweight delicate objects which require fine control when grasping. Sensorizing such grippers is often challenging due to the highly deformable surfaces. We propose a novel sensing approach which uses highly flexible latex bladders. By measuring changes in the air pressure of the bladders, normal force and longitudinal strain can be measured. These sensors have been integrated into a 'Magic Ball' origami gripper to provide both tactile and proprioceptive sensing. The sensors show reasonable sensitivity and repeatability, are durable and low-cost, and can be easily integrated into the gripper without affecting performance. When the sensors are used for classification, they enabled identification of 10 objects with over 90% accuracy, and also allow failure to be detected through slippage detection. A control algorithm has been developed which uses the sensor feedback to extend the capabilities of the gripper to include both delicate and strong grasping. It is shown that this closed loop controller enables delicate grasping of potato chips; 80% of those tested were grasped without damage. © 2020 IEEE.

Optical sensors have recently been proposed for sensing bending, linear strains and external forces in soft actuators. However, the susceptibility of these sensors to a number of stimuli makes it difficult to comprehend the resulting data output. We address this challenge through the introduction of a low-cost flexible bending sensor based upon the abrasion of optical channels. Such sensors are responsive to bending while being insensitive to internal pressure or external forces. The developed sensor is integrated into a soft pneumatic finger in order to obtain feedback of its curvature. We further demonstrate that the sensor is insensitive to normal forces applied on a blocked finger. Through this work, we propose a simple, low-cost sensor development technique towards addressing the challenge of decoupling forces and deformations in soft robots.

This paper presents the theory, design, and development of an innovative shear sensor using force sensitive resistors (FSR) and two soft silicone layers that is intended to allow shear forces applied to skin to be measured. The sensor is being developed to better understand the shear forces applied to skin during patient transfers. The sensor is constructed using four FSRs arranged in a two by two matrix and secured between the two silicone layers. The silicone layers include features to secure the FSRs in place and concentrate the force applied to the sensor to the center of the FSR pads. The preliminary results show that the sensor allows the measurement of normal forces of up to 4.9 N applied to the 4.5cm square sensor to be measured with an R2 of 0.996. The results also show that the sensor can measure shear forces of up to 1.5 N with an R2 of 0.981. The results show the sensor has a linear response to both normal and shear forces. Future work is required to further analyze the performance of this novel sensor.

Capturing large objects of unknown shape and orientation remains a challenge for most robotic grippers. We present a highly under-actuated gripper well suited for this task. Prior work shows two primary limitations to these grippers: the grip force of each link tends to decrease as the number of links increases, and the stability of an under-actuated linkage depends on the configuration of the links so grippers with many links are unlikely to be stable for arbitrary surfaces. We address these concerns by implementing two complementary methods of stabilization: using high-friction materials and scaling forces into the surface. We show that gecko-inspired adhesives provide an adhesion-controlled friction that can stabilize the gripper and improve grasp performance without the need of large normal forces. The under-actuated linkages also conform around arbitrary shapes and provide capability beyond prior adhesion-based grippers. With these high-friction interfaces, we show highly under-actuated linkages successfully grasp in many configurations without strict stability. The gripper is capable of holding over 30 N and consists of two tendon driven linkages that are each 65 cm long. This type of gripper is well suited for tasks without a predefined target geometry or orientation such as satellite servicing.

This study proposes a softness presentation method for when the finger slides on a hard touch panel. Herein, an electrostatic tactile display was made to present a friction stimulus, the frequency of which was changed by virtue of the normal force and speed of the finger. Such a stimulus imitates the stick-slip phenomenon that occurs between soft materials. In the experiment where four types of stimulus conditions were ranked, one of which was a control condition with no active friction stimulus, the new stimulus and previous method that presented a constant low-frequency friction were subsequently determined to be the softest among the four stimulus condition types.

Using a force-controlled robotic platform, we investigated the contact mechanics and psychophysical responses induced by negative and positive modulations in normal force during passive dynamic touch. In the natural state of the finger, the applied normal force modulation induces a correlated change in the tangential force. In a second condition, we applied talcum powder to the fingerpad, which induced a significant modification in the slope of the correlated tangential change. In both conditions, the same ten participants had to detect the interval that contained a decrease or an increase in the pre-stimulation normal force of 1 N. In the natural state, the 75% just noticeable difference for this task was found to be a ratio of 0.19 and 0.18 for decreases and increases, respectively. With talcum powder on the fingerpad, the normal force thresholds remained stable, following the Weber law of constant just noticeable differences, while the tangential force thresholds changed in the same way as the correlation slopes. This result suggests that participants predominantly relied on the normal force changes to perform the detection task. In addition, participants were asked to report whether the force decreased or increased. Their performance was generally poor at this second task even for above-threshold changes. However, their accuracy slightly improved with the talcum powder, which might be due to the reduced finger-surface friction.