A Novel Biomimetic Compliant Structural Skin Based on Composite Materials for Biorobotics Applications.

Biorobotics is increasingly attracting engineers worldwide, due to the high impact this field can have on the society. Biorobotics aims at imitating or taking inspiration from mechanisms and strategies evolved by animals, including their locomotion abilities in real scenarios, such as swimming, running, crawling, and flying. However, the development of skin-mimicking structures, allowing protection without hindering artifacts' movements, has been rarely addressed. Skin-mimicking structures play a key role for biomimetic robots that have to move in unstructured environments. Currently most of the skin used for robots in engineering adopts soft materials or bellow structures to enable both structural deformation and protection. However, the elastic nature of the former can produce support failure and increasing strain with deformation, while the humpy surface of the latter reduces the interactive performance with the environment. Herein, we designed a novel compliant structure for biorobots' skin, fabricated through a special configuration of both soft and rigid materials to reproduce attributes provided by natural epithelial structures. The presented skin has a simple fabrication process, as well as it is cost effective. The structure of this skin includes a thin conical shape where rigid iron rings are wrapped by soft polyester fabrics, allowing a theoretically zero elastic modulus when bended and stretched. The dimension of fabrics was specified to allow rigid rings having a certain range of free rotation and translation. The possibility of free bending and stretching of the structure was implemented by overcoming low sliding friction of adjacent rings. To empirically test the effectiveness of the proposed structure, a model, including 20 segments, was also fabricated. Experimental results from the bending tests, both in aerial and underwater environments, as well as from the folding tests, demonstrated the successful performance of the skin prototype in terms of low resistance and energy consumption. Finally, the proposed highly compliant structural skin was mounted and tested on a fish robot previously developed by authors, to further show its effectiveness.

Trajectory Tracking Control for Flexible-Joint Robot Based on Extended Kalman Filter and PD Control.

The robot arm with flexible joint has good environmental adaptability and human robot interaction ability. However, the controller for such robot mostly relies on data acquisition of multiple sensors, which is greatly disturbed by external factors, resulting in a decrease in control precision. Aiming at the control problem of the robot arm with flexible joint under the condition of incomplete state feedback, this paper proposes a control method based on closed-loop PD (Proportional-Derivative) controller and EKF (Extended Kalman Filter) state observer. Firstly, the state equation of the control system is established according to the non-linear dynamic model of the robot system. Then, a state prediction observer based on EKF is designed. The state of the motor is used to estimate the output state, and this method reduces the number of sensors and external interference. The Lyapunov method is used to analyze the stability of the system. Finally, the proposed control algorithm is applied to the trajectory control of the flexible robot according to the stability conditions, and compared with the PD control algorithm based on sensor data acquisition under the same experimental conditions, and the PD controller based on sensor data acquisition under the same test conditions. The experimental data of comparison experiments show that the proposed control algorithm is effective and has excellent trajectory tracking performance.

A Muscle-Specific Rehabilitation Training Method Based on Muscle Activation and the Optimal Load Orientation Concept.

Training based on muscle-oriented repetitive movements has been shown to be beneficial for the improvement of movement abilities in human limbs in relation to fitness, athletic training, and rehabilitation training. In this paper, a muscle-specific rehabilitation training method based on the optimal load orientation concept (OLOC) was proposed for patients whose motor neurons are injured, but whose muscles and tendons are intact, to implement high-efficiency resistance training for the shoulder muscles, which is one of the most complex joints in the human body. A three-dimensional musculoskeletal model of the human shoulder was used to predict muscle forces experienced during shoulder movements, in which muscles that contributed to shoulder motion were divided into 31 muscle bundles, and the Hill model was used to characterize the force-length properties of the muscle. According to the musculoskeletal model, muscle activation was calculated to represent the muscle force. Thus, training based on OLOC was proposed by maximizing the activation of a specific muscle under each posture of the training process. The analysis indicated that the muscle-specific rehabilitation training method based on the OLOC significantly improved the training efficiency for specific muscles. The method could also be used for trajectory planning, load magnitude planning, and evaluation of training effects.

Kinematic design considerations for minimally invasive surgical robots: an overview.

BACKGROUND: Kinematic design is a predominant phase in the design of robotic manipulators for minimally invasive surgery (MIS). However, an extensive overview of the kinematic design issues for MIS robots is not yet available to both mechanisms and robotics communities. METHODS: Hundreds of archival reports and articles on robotic systems for MIS are reviewed and studied. In particular, the kinematic design considerations and mechanism development described in the literature for existing robots are focused on. RESULTS: The general kinematic design goals, design requirements, and design preferences for MIS robots are defined. An MIS-specialized mechanism, namely the remote center-of-motion (RCM) mechanism, is revisited and studied. Accordingly, based on the RCM mechanism types, a classification for MIS robots is provided. A comparison between eight different RCM types is given. Finally, several open challenges for the kinematic design of MIS robotic manipulators are discussed. CONCLUSIONS: This work provides a detailed survey of the kinematic design of MIS robots, addresses the research opportunity in MIS robots for kinematicians, and clarifies the kinematic point of view to MIS robots as a reference for the medical community.