User's Force Research Articles

Upper-Limb Rehabilitation Robot: A Measure of Intent Detection for Robot Aided Active Therapy Exercise

<h3>Research Objectives</h3> In robot-aided rehabilitation of post-stroke patients with upper limb impairment, robotic device must allow patient's effort in performing exercises. To estimate such effort, user's force exerted on robotic device can be used during active exercises. To validate use of force exerted by user/wearer by comparing with EMG signals as a measure of intent detection in robot-aided active therapy on rehabilitation robot, in this research, user's interactive force with robot was measured and compared with user's muscle activity (EMG) during elbow flexion-extension performed by an upper-limb rehabilitation robot (u-Rob). This physiological measure will help design rehab robot centering patient's need and level of impairment. Furthermore, it can give an indication of spastic behavior during rehab exercises. <h3>Design</h3> Experimental study of robot-aided therapy to observe force values with EMG values, leading to use force as a measure of intent detection. <h3>Setting</h3> Protocol: Elbow flexion/extension (0-120 deg) motion. Experiments (passive and active therapy exercise, five trials/exercise) were conducted with healthy subject in seated position wearing the robot. <h3>Participants</h3> 2 healthy males and 1 healthy female. <h3>Interventions</h3> Elbow flexion/extension (0-120 deg) motion. Experiments (passive and active therapy exercise, five trials) were conducted subject in seated position wearing the robot. <h3>Main Outcome Measures</h3> Force exerted by the participant and participant's EMG <h3>Results</h3> Significant amount of force is exerted during active exercise and significant amount of EMG activity is observed during active exercise. Besides, looking at the torque, it is seen that during active rehab exercise, robot has to contribute lesser torque than in passive exercise. <h3>Conclusions</h3> User-robot interactive forcesdetected by sensor can be used as a measure of intent detection during robot-aided active exercise. Moreover, measured forces can also be observed from muscle activity. It may give an idea of subject's spastic behavior. <h3>Author(s) Disclosures</h3> N/A.

Experimental analysis of user forces by test bench and manual hammer drill experiments with regard to vibrations and productivity

The user's forces have great influences on the load and on the drilling process of hammer drills. Hence, these influences must be known in product development for reproducible testing on test benches. Furthermore, manufacturers focus on developing hammer drills, which improve productivity and force-efficiency during application. Therefore, the aim of this study is to investigate the influences of the forces exerted by the user on a hammer drill when drilling in concrete. For this purpose, the applied forces and the resulting vibrations of three users drilling in different directions at different force levels were analyzed and compared with an automated test bench, which is equipped with a hand-arm model. It can be shown that the commercially available hand-arm model cannot reproduce the vibration properties of the subjects. Further findings from the experiment are that the subjects applied lateral forces, which do not occur adequately on the test bench. The feed force has an influence on the rate of penetration and there is a force-efficient operating point, which differs from the highest rate of penetration. The results indicate that further investigations need to be carried out to analyze user influences on a broader scale.

A User Study on Personalized Stiffness Control and Task Specificity in Physical Human–Robot Interaction

An ideal physical Human-Robot Interaction (pHRI) should offer the users robotic systems that are easy to handle, intuitive to use, ergonomic and adaptive to human habits and preferences. But the variance in the user behavior is often high and rather unpredictable which hinders the development of such systems. This article introduces a Personalized Adaptive Stiffness controller for pHRI which is calibrated for the user's force profile and validates its performance in an extensive user study with 49 participants on two different tasks. The user study compares the new scheme to conventional fixed stiffness or gravitation compensation controllers on the 7-DOF KUKA LWR IVb by employing two typical joint-manipulation tasks. The results clearly point out the importance of considering task specific parameters and human specific parameters while designing control modes for pHRI. The analysis shows that for simpler tasks a standard fixed controller may perform sufficiently well and that respective task dependency strongly prevails over individual differences. In the more complex task, quantitative and qualitative results reveal differences between the respective control modes, where the Personalized Adaptive Stiffness controller excels in terms of both performance gain and user preference. Further analysis shows that human and task parameters can be combined and quantified by considering the manipulability of a simplified human arm model. The analysis of user's interaction force profiles confirms this finding.

Segmentation of Bimanual Virtual Object Manipulation Tasks Using Multifinger Haptic Interfaces

This paper describes data processing using a haptic interface for virtual object grasping tasks. The haptic interface known as MasterFinger-2 (MF-2) is used. This haptic device enables the simulation of object manipulation using the thumb and index finger, which are inserted within thimbles located at the far end of the haptic interface. The experiments were conducted using a setup that provides the operator with two MF-2s. This setup enables bimanual virtual object manipulation. The haptic device provides data about the angular position of all joints and data from four contact sensors located within the thimbles. The values obtained from the angular positions of the joints enable a calculation of the position and orientation of the thimbles, whereas the values obtained from the contact sensors are used to formulate an approximate calculation of the user's force during object manipulation. This information regarding forces enables the segmentation of manipulation tasks and is essentially based on the rising edges produced by the contact sensor signals. After performing task segmentation, the state of the task in progress is detected. This facilitates improvements in user interaction because restrictions can be established in the relationships between the objects that change dynamically depending on the stage of manipulation. This information allows for an improvement in the realism of the simulation because the forces reflected take into account how the relationships between objects vary over the course of the task. Task segmentation is also used to ascertain objects' physical properties. These features are then used to simulate virtual objects with the same properties.

A Control Framework to Generate Nonenergy-Storing Virtual Fixtures: Use of Simulated Plasticity

Some recent studies have addressed a class of human-machine coordination employing ldquovirtual fixtures,rdquo which are computer-generated walls or guides presented through haptic devices for assisting precise path tracing and for preventing the entry to specified regions. This paper presents the concept and control algorithms of a new class of virtual fixtures that is based on simulated plasticity. The plasticity-based virtual fixtures act as hard walls as long as the user's force is smaller than a predetermined yield force, but the user can deviate from the fixtures by intentionally producing a force larger than the yield force. As a characteristic of plasticity, the proposed virtual fixtures do not store elastic energy; the reaction force from the fixture almost always opposes the user's motion to decelerate the motion. Thus, the plasticity-based virtual fixtures are expected to be useful in some applications where safety is an utmost priority. This paper presents control algorithms for realizing the concept of plasticity-based virtual fixtures, addressing technical challenges in treating discontinuous nature of plasticity in discrete-time systems. The algorithms were demonstrated through experiments using impedance-type and admittance-type haptic devices.

2P2-B40 フィジカルマンマシンインタラクションを実現するアクティブマウスの開発 : 第4報:アクティブマウスによるフィジカルマンマシンインタラクションの実現

Considering the increasing needs of technology on virtual reality, we focused on interfaces that can present force and motion, and many devices have been developed. In this paper, we report a new device called Active Mouse to realize man-machine-interaction without losing portability and generality. This mouse is equipped with a force sensor that gets three directional values of user's force. In addition we developed a new differential mechanism for a trackball and two electronic motors that enable the mouse move in any directions. We developed System of communication and control with PSoC and USB device. From the basic experimental results, it was found that this mouse can present the maximum force of 5N. In addition, from the application test, it realized man-machine interaction. As a result, a potential of this mouse is shown as a practical haptic device.

Effect of Servo-System on Haptic Interface.

Multi-media services such as audio and visual media are advanced rapidly. In addition to them, physical force information is expected as the next service, which may realize virtual reality service. Many reserches concerning the haptic interface as the force display have been reported. However, as they have not been studied specially from the control view point, control problems have not been clarified systematically. The purpose of this paper is to clarify the control problems of the haptic interface systematically, which includes not only the realization of the force display but also its stability and limitation. In this paper, two major control algorithms are investigated. The first type is the position control type, which realizes the position corresponding to user's force in consideration of the virtual environment dynamics. The second type is the force control, which realizes the force corresponding to operator's finger position. The following results are obtained. (1) Position control type: This type can realize the stable system for applied force. However, the force display does not show sharp linearity because it does not consider the force balance between the operator's finger and the interface. As the virtual environment dynamics must be used for realizing the Free Space, the unstable phenomenon occurs the continuation of the dynamic parameter is not guaranteed between the Free space and the Constrained Space. (2) Force control type: This system shows excellent performance as the force display because it actually generates the force by itself. However, the unstable phenomenon occurs when the force display becomes larger in relation to the user's finger reflecting force.