This work faces the redundancy problem, a central concern in robotics, in a particular force-producing task by using muscle synergies to simplify the control. We extracted muscle synergies from human electromyograph signals and interpreted the physical meaning of the identified muscle synergies. Based on the human analysis results, we hypothesized a novel control framework that can explain the mechanism of the human motor control. The framework was tested in controlling a pneumatic-driven robotic arm to perform a reaching task. This control method, which uses only two synergies as manipulated variables for driving antagonistic pneumatic artificial muscles to generate desired movements, would be useful to deal with the redundancy problem; thus, suggesting a simple but efficient control for human-like robots to work safely and compliantly with humans. 相似文献
Rather severe parametric uncertainties and uncertain nonlinearities exist in the dynamic modeling of a parallel manipulator driven by pneumatic muscles. Those uncertainties not only come from the time-varying friction forces and the static force modeling errors of pneumatic muscles but also from the inherent complex nonlinearities and unknown disturbances of the parallel manipulator. In this paper, a discontinuous projection-based adaptive robust control strategy is adopted to compensate for both the parametric uncertainties and uncertain nonlinearities of a three-pneumatic-muscles-driven parallel manipulator to achieve precise posture trajectory tracking control. The resulting controller effectively handles the effects of various parameter variations and the hard-to-model nonlinearities such as the friction forces of the pneumatic muscles. Simulation and experimental results are obtained to illustrate the effectiveness of the proposed adaptive robust controller. 相似文献
Artificial muscles are reported in which reduced graphene oxide (rGO) is trapped in the helical corridors of a carbon nanotube (CNT) yarn. When electrochemically driven in aqueous electrolytes, these coiled CNT/rGO yarn muscles can contract by 8.1%, which is over six times that of the previous results for CNT yarn muscles driven in an inorganic electrolyte (1.3%). They can contract to provide a final stress of over 14 MPa, which is about 40 times that of natural muscles. The hybrid yarn muscle shows a unique catch state, in which 95% of the contraction is retained for 1000 s following charging and subsequent disconnection from the power supply. Hence, they are unlike thermal muscles and natural muscles, which need to consume energy to maintain contraction. Additionally, these muscles can be reversibly cycled while lifting heavy loads. 相似文献
Pneumatic artificial muscle (PAM) has highly nonlinear and time-varying behavior due to gas compression and nonlinear elasticity of the bladder containers. Hence, it is difficult to achieve excellent tracking performance when using classical control methods. This study proposes a Takagi–Sugeno (T–S) fuzzy model-based control for improving control performance. The proposed approach decomposes the model of a nonlinear system into a set of linear subsystems. This allows, the T–S fuzzy model-based controller to use simple linear control techniques providing a systematic framework for the design of a state feedback controller. Stability analysis is carried out using Lyapunov direct method. The powerful LMI Toolbox in MATLAB is employed to solve linear matrix inequalities (LMIs) to obtain the controller gains. Experimental results verified that the proposed controller can achieve excellent tracking performance under different disturbances. 相似文献
The three-compartment model (3CM) was validated previously for prediction of endurance times by modifying its fatigue and recovery rates. However, endurance times do not typically represent work demands, and it is unknown if the current version of the 3CM is applicable for ergonomics analysis of all occupational tasks. The purpose of this study was to add biological fidelity to the 3CM, and validate the model against a series of submaximal force plateaus. The fatigue and recovery rates were modified to represent graded physiological motor unit characteristics (termed 3CMGMU). In nine experiments of submaximal efforts, the 3CMGMU produced a root-mean squared difference (RMSD) of 4.1 ± 0.5% MVC over experiments with an average strength loss (i.e. fatigue) of 31.0 ± 1.1% MVC. The 3CMGMU model performed poorly for endurance tasks. The 3CMGMU model is an improvement for evaluating submaximal force patterns consisting of intermittent muscle contractions of the hand and forearm.
Practitioner Summary: We modified an existing fatigue model using known physiological properties in order to predict fatigue during nine different submaximal force profiles; consistent with efforts seen in industrial work. We expect this model to be included in digital human modelling software, for the assessment of repetitive work and muscle fatigue in repetitive tasks.
Social Media Summary: The proposed model has applications for estimating task fatigue in proactive ergonomic analyses of complex force patterns using digital human models. 相似文献
Twenty-seven subjects completed 2-min typing tasks using four typing styles: right-hand holding/typing (S-thumb) and two-hand typing at three heights (B-low, B-mid and B-high). The styles had significant effects on typing performance, neck and elbow flexion and muscle activities of the right trapezius and several muscles of the right upper limb (p < 0.0001 by repeated-measure analysis of variance). The subjects typed the fewest words (error-adjusted characters per minute: 78) with the S-thumb style. S-thumb style resulted in similar flexion angles of the neck, elbow and wrist, but significantly increased muscle activities in all tested muscles compared with the B-mid style. Holding the phone high or low reduced the flexion angles of the neck and right elbow compared with the B-mid style, but the former styles increased the muscle activity of the right trapezius. Right-hand holding/typing was not a preferable posture due to high muscle activities and slow typing speed.
Practitioner Summary: Right-hand holding/typing was not favoured, due to increased muscle activities and slower typing speed. Holding the phone high or low reduced the flexion angles of the neck and right elbow, but the former styles increased the muscle activity of the right trapezius compared with holding the phone at chest level. 相似文献
A new method is reported for human biodynamic measurement, which includes an improved motion measurement system via virtual marker technology and a wavelet algorithm to extract muscle activities from electromyography signals in vivo. Four channels of electromyography signals and twelve virtual markers motion data were collected when the subject did a standard gait experiment. Then, a wavelet algorithm was used to process raw electromyography signals and to extract muscle activity features. The results demonstrated that the proposed method could shorten the motion measurement experiment time and improve the measurement accuracy. The proposed wavelet algorithm could efficiently extract muscle activity features from electromyography signals. The reported method may be potentially used for the human biodynamic research and clinical biomechanics. Possible further improvements for this method are also discussed. 相似文献