Grasping Force Research Articles

Optimization of an aluminum alloy anti-collision side beam hot stamping process using a multi-objective genetic algorithm

The process parameters of aluminum alloy hot stamping are essential for product forming quality. In the case of an anti-collision side beam inside car doors, the finite-element model of aluminum alloy hot stamping is set up, and the forming quality is investigated under an ordinary process condition. The blank hold force (BHF) has a significant impact on the forming quality in hot stamping. Using the Latin hypercube method to sample the simulation data points and the finite-element (FE) model to calculate the forming quality indices of the data points according to the response value of the indices, the quadratic response surfaces between the process parameter inputs and the forming quality indices are initialized. Using the multi-objective genetic algorithm NSGA-II (non-dominated sorting genetic algorithm) to optimize the responses of the process parameters, the Pareto solutions corresponding to combinations of the blank hold force and stamping speed are obtained. Finally, based on the optimal process parameters, stamping tests are carried out. Compared with the results of the stamping trial and numerical simulation, it is demonstrated that the finite-element model can predict forming defects and be consistent with the actual condition and that the optimization procedure proposed in the paper is feasible.

Grasping force controller for parallel grip with fuzzy rules emulated networks

A grasping force regulation for industrial parallel grips is developed without any requirement of mathematic model regarding to the contact mechanism and system dynamic. The physical system including the grasping dynamic and contact mechanism is considered as a class of unknown nonlinear discrete-time systems. An adaptive network called multi-input fuzzy rules emulated network (MiFREN) is implemented as the controller. This control scheme is performed by if-then rules which can be directly defined by human knowledge regarding to the gripper’s specification and objects. The learning algorithm based on gradient search is developed to tune all adjustable parameters inside MiFREN. The system performance and stability can be guaranteed by the time-varying learning rate. An industrial parallel grip SCHUNK-WSG 50 with the proposed controller demonstrates the performance via the experimental setup. Furthermore, the performance can be spontaneously improved within the next iteration of the learning process.

A Grasping Force Optimization Algorithm for Multiarm Robots With Multifingered Hands

The computation of the grasping forces for a multiarm robotic manipulation system (e.g., an anthropomorphic bimanual system) is considered in this paper. This problem is formulated as a convex optimization problem, also considering joint torque constraints. An algorithmic solution suitable for online implementation is presented, which allows a substantial reduction in the computational load by adopting a compact formulation and dynamically decreasing the number of active torque constrains. Moreover, for the case of a bimanual manipulation system, a suboptimal single-hand optimization algorithm is proposed and compared with that providing the optimal solution. Finally, a new algorithm for a valid initial-point evaluation is proposed. The effectiveness of the described methods has been tested in a simulation case study where the grasping forces of a humanoid torso equipped with two five-finger robotic hands are modified online to handle a load with a time-varying mass.

Force Feedback Manipulating System for Neurosurgery

For the application to the resection of brain tumor, force detecting micro gripper and force feedback system has been developed. Grasping force and pulling force at the gripper are transmitted to the master operating system where the surgeon feel the gr ipping force as force resistance and pulling force as friction on the finger surface.The feeling at the master operator has been investigated through the gripping test on soft materials in various hardness applying force reflection bilateral control program. Topics: OS2: Medical devices and medical tools.

A Noninvasive Neuroprosthesis Augments Hand Grasp Force in Individuals with Cervical Spinal Cord Injury: The Functional and Therapeutic Effects

Objectives. The primary purpose of this study was to evaluate myoelectrically controlled functional electrical stimulation (MeCFES) for enhancing the tenodesis grip in people with tetraplegia. The second aim was to estimate the potential number of candidates for the MeCFES device. The application of MeCFES provides the user with direct control of the grasp force as opposed to triggered FES systems. Methods. Screening 253 medical records of C5 to C7 spinal cord injury resulted in 27 participants who trained activities of daily living for 12 × 2 hours, using the MeCFES. Hand function was evaluated by the Action Research Arm Test (ARAT). Primary outcome was the ARAT change score with/without the device, before/after the intervention period. Secondary outcome was the number of positive or clinically relevant change scores with respect to the cohort. Results. The MeCFES improved hand test score in 63% of the subjects at first application. Training resulted in a significant therapeutic effect, which resulted in an overall increase of hand function in 89% of the participants and 30% experienced a clinically relevant change (6 points or more). Conclusions. Clinical relevance was found both as an assistive aid and as a therapeutic tool in rehabilitation. The therapeutic effect deserves further investigation in clinical studies.

Small Size Forceps with High Grasping Force for Flexible Endoscopic Surgery

Small Size Forceps with High Grasping Force for Flexible Endoscopic Surgery

Large Grasp Force Hand with High Compliance during High Speed Phase

This paper presents a back-drivable two-fingered four-degree of freedom hand that can generate a large grasping force of 120 N and perform a high speed motion of larger than 750 °/s. All fingers are 98 mm in length and the weight of the hand is 1.2 kg. The hand can generate a large grasp force with a new force-magnification mechanism. The force-magnification mechanisms installed in our previous hands need a non-backdrivable element so that their high-speed drive mechanisms cannot be back-driven when the force-magnification mechanisms are activated, which results in low compliance. The new force-magnification mechanism in this paper uses a rack and pinion gear connection mechanism to establish the drive connection with the high-speed drive mechanism only when it is activated. Therefore, the high-speed drive mechanism can be back driven keeping high compliance. However, when the tooth crests of the rack hits that of the pinion gear, the connection mechanism is jammed. Therefore, a rack gear tilting mechanism is also proposed.

A Robot Finger Design Using a Dual-Mode Twisting Mechanism to Achieve High-Speed Motion and Large Grasping Force

A dual-mode robot finger is proposed to achieve a high-speed motion and large grasping force with a single motor. The robot finger has two actuator modes, which consist of the speed mode and the force mode. Based on the geometric analysis of each mode, the main design parameters of the proposed robot finger are derived, and their effectiveness is verified by simulations. In addition, using experiments with a prototype of a robot finger, the validity of the proposed approach is demonstrated.

Hand Grasp Force during Static Teeth Clenching and Nonclenching

Hand Grasp Force during Static Teeth Clenching and Nonclenching

On Computing Reliable Optimal Grasping Forces

This paper presents algorithms for optimal grasping forces. The previous work reveals that contact forces with minimal sum or maximum of normal force components can be written as positive combinations of primitive contact forces, to which the corresponding primitive contact wrenches express the required resultant wrench as their positive combination with minimum coefficients in terms of the L1 or L∞ metric. On this basis, we first propose an algorithm to compute such a set of primitive contact forces and the minimum contact forces. Moreover, considering the uncertainty in the actual friction coefficient, we develop another algorithm to determine the minimum required friction coefficient and the corresponding minimum contact forces within a given limit on their magnitude so that such contact forces are more reliable in practice. As our algorithms do not rely on any general optimization technique, they are very efficient and easy to implement. These algorithms can also be used in grasp quality evaluation and optimal grasp planning.

Micro Forceps with Large Grasp Force for Flexible Endoscopy

Micro Forceps with Large Grasp Force for Flexible Endoscopy

Comparing Study on Real Drawbead and Equivalent Drawbead Based on Finite Element Analysis

The dynamic explicit finite element software DYNAFORM was used to simulate the real and equivalent drawbead model. Analyzed the influence of the blank hold force (BHF) and virtual velocity on blank’s deformation behavior after passing through drawbead, compared the results of the FE simulation. The simulation results were confirmed by experiments. The study shows that the equivalent drawbead model can’t simulate the blank’s behavior precisely when it passing the real drawbeads, the effect of BHF on real drawbead model is larger than equal drawbead model; the proper range of virtual velocity was obtained at the same time.

리클라이너 용 섹터기어의 파인 블랭킹 성형을 위한 금형의 최적화

To optimization of mlod for fineblanking forming of sector gear of recliner, it was analyzed the effect of clearance, V-ring height, V-ring position, blank holding force and counter punch force. In case of 0.003 mm of clearancs, the finest shear plane was obtained, but optimization between die and punch clearance was 0.005 mm. The height of V-ring was 0.7 mm. In case of increasing of hold force, the size of shear plane got better and the decrement of thickness became smaller. Both the size of shear plane and the decrement of thickness increased according to increasing of counter punch force.

Distributed Contact Model for Indeterminate Grasp Force Analysis towards Heavy-Duty Manipulation

This paper presents a new contact model to describe the contact constraints for heavy-duty manipulation. This contact model considers the contact area as a surface, which can translate three-dimension forces and torques. The contact deformations which are resulting from the large contact forces cannot be ignored. Distributed linear elastic contact model is adopted to describe the relationship between contact force and contact deformation. A case study is carried out in this paper based on this contact model for the grasp force analysis of heavy-duty manipulators.

Estimation of Grasping Force from Features of Intramuscular EMG Signals with Mirrored Bilateral Training

This study investigates the use of features extracted from intramuscular electromyography (EMG) for estimating grasping force in the ipsilateral and contralateral (mirrored) hand, during bilateral grasping tasks. This is relevant since force estimation using mirror tasks is a potentially useful pathway for the clinical training of unilateral amputees. Bilateral grasping force and intramuscular EMG (wire electrodes) of the right forearm were measured in 10 able-bodied subjects. The features extracted from the EMG signal were the root mean square, the global discharge rate, the standard sample entropy, and the constraint sample entropy (CSE). The association between the EMG features and force was modeled using a first-order polynomial model, a second-order exponential model, and an artificial neural network (ANN). The accuracies of estimation of ipsilateral and mirrored grasping force were not significantly different (e.g., R(2) = 0.89 ± 0.02 for ipsilateral and 0.88 ± 0.017 for mirrored, when using CSE and the ANN). It was concluded that it is possible to use just one channel of intramuscular EMG for force estimation. This result suggests that intramuscular EMG signals may be suitable for proportional myoelectric control and that training of the association between intramuscular EMG features and force can be performed using mirror tasks, which is a needed condition for applications in unilateral amputees.

Impaired force control during food holding and biting in subjects with tooth‐ or implant‐supported fixed prostheses

Our goal here was to assess the ability of subjects with their natural teeth (natural), bimaxillary tooth-supported bridges (bridge) and bimaxillary implant-supported bridges (implant) to control the low contact and high biting forces associated with holding and splitting food between the teeth. Ten subjects in each of these groups performed a task involving holding and splitting morsels of food with different degrees of hardness (biscuits and peanuts) between a pair of opposing central incisors. The hold force employed by the implant group was significantly higher and more variable than the corresponding force exerted by the bridge group, whereas the natural group used lowest and least variable force. For all three groups, the split force was higher and the split phase duration longer with peanuts than for biscuits. In the case of the natural group, a significantly higher rate of force increase (peak force rate) was observed when splitting peanuts when compared with biscuits, whereas no such difference could be seen for the other two groups. These findings demonstrate that individuals with bimaxillary tooth- or implant-supported bridges (in whom sensory information provided by the periodontal mechanoreceptors is impaired or missing) are unable to apply low-hold forces at the levels of individuals with natural teeth or to adapt the rate of the split force to the hardness of the food. We thus conclude that adequate sensory information from periodontal mechanoreceptors is essential for normal control of both low contact and high biting forces.

Regulation of Catch Bonds by Rate of Force Application

The current paradigm for receptor-ligand dissociation kinetics assumes off-rates as functions of instantaneous force without impact from its prior history. This a priori assumption is the foundation for predicting dissociation from a given initial state using kinetic equations. Here we have invalidated this assumption by demonstrating the impact of force history with single-bond kinetic experiments involving selectins and their ligands that mediate leukocyte tethering and rolling on vascular surfaces during inflammation. Dissociation of bonds between L-selectin and P-selectin glycoprotein ligand-1 (PSGL-1) loaded at a constant ramp rate to a constant hold force behaved as catch-slip bonds at low ramp rates that transformed to slip-only bonds at high ramp rates. Strikingly, bonds between L-selectin and 6-sulfo-sialyl Lewis X were impervious to ramp rate changes. This ligand-specific force history effect resembled the effect of a point mutation at the L-selectin surface (L-selectinA108H) predicted to contact the former but not the latter ligand, suggesting that the high ramp rate induced similar structural changes as the mutation. Although the A108H substitution in L-selectin eliminated the ramp rate responsiveness of its dissociation from PSGL-1, the inverse mutation H108A in P-selectin acquired the ramp rate responsiveness. Our data are well explained by the sliding-rebinding model for catch-slip bonds extended to incorporate the additional force history dependence, with Ala-108 playing a pivotal role in this structural mechanism. These results call for a paradigm shift in modeling the mechanical regulation of receptor-ligand bond dissociation, which includes conformational coupling between binding pocket and remote regions of the interacting molecules.

The Influence of Exposure Amount on the Persistence of Short-Term, Haptically Acquired Sensorimotor Memorial Representations

This study investigates the influence that the amount of exposure has on the persistence of sensorimotor memories. Participants acquired memories of an unexpectedly heavy object in one of four groups that varied in the number lifts of the object they each performed. All participants followed this acquisition period with retention lifts immediately and after 2-second and 10-second intervals, as well as after 15 minutes and 24 hours. Grasp force profiles were evaluated for the maintenance of memory-dependent adaptations. A lack of any group effects indicates that the quantity of exposure offers the sensorimotor memory system no temporal advantage in the maintenance of short-term representations. The results are discussed in light of the possibility that, within a short time frame, only the information from the preceding lift has functional relevance to the current lift.

Experimental Study of Micro Deep Drawing for H62 Brass

In this paper, the influence of grain size and blank hold force on micro deep drawing stress and displacement are studied by self-made device. The results show that drawing stress decreases and elongation rate increases with the increase of grain size, the concentrated force area of cylinder-shaped part is transferred from the area punch fillet to die fillet area. Twin grain ratio and twinning degree near the punch fillet are increasing. Twin grain distribution becomes uneven with the increase of grain size. In micro deep drawing, the displacement increases with the increase of blank hold force, meanwhile, forming stress almost remains constant. The flange wrinkling can be inhibited.

Frictional aging, de-aging, and re-aging in a monolayer-coated micromachined interface

Measurements on monolayer-coated polycrystalline silicon surfaces have shown that the static friction coefficient ${\ensuremath{\mu}}_{s}$ strongly depends on loading parameters including hold time and normal hold force by Corwin and de Boer [J. Microelectromech. Syst. 18, 250 (2009)]. In that work, ${\ensuremath{\mu}}_{s}$ was measured by keeping the tangential force constant and lowering normal force until motion occurred. Results indicated that ${\ensuremath{\mu}}_{s}$ also depends strongly on normal force ramp-down rate. Here, we postulate that if the normal load is lowered instantaneously, the time for the block to begin moving, the ``release time'' ${t}_{r}$, will be greater than the inertial response time, which is on the order of $5\text{ }\ensuremath{\mu}\text{s}$. We measure the release time and find that it spans nearly six decades from less than $100\text{ }\ensuremath{\mu}\text{s}$ to almost 50 s. Release time depends on the loading and unloading history through all three of the parameters varied: hold time, hold force, and release force. An empirical model incorporating all three of these parameters fits the release time data over the full range. Release time decreases after the contacting surfaces are held together at increasing hold force levels and this qualitatively explains a previous observation that static friction aging is suppressed with increasing normal force at a fixed tangential load in this interfacial system. We further quantitatively relate the previous ${\ensuremath{\mu}}_{s}$ loading dependence on all three parameters to the release time model established here by introducing a ``re-aging'' parameter. This work firmly establishes that release time is a more fundamental parameter than the static friction coefficient and is the origin of static friction coefficient dependencies in this micromachined interface.