[Show abstract][Hide abstract] ABSTRACT: A number of issues that exist in common fracture reduction surgeries can be mitigated by robot-assisted fracture reduction. However, the safety of patients and the performance of the robot, which are closely related to the muscle forces, are important indexes that restrict the development of robots. Though researchers have done a great deal of work on the biomechanics of the musculoskeletal system, the dynamics of the musculoskeletal system, particularly the aspects related to the function of the robot, is not well understood. For this reason, we represent the complex biological system by establishing
a dynamic biomechanical model based on the Hill muscle model and the Kane method for the robot that we have developed and the musculoskeletal system. We analyzed the relationship between the motion and force of the bone fragments and the robot during a simulation of a robot-assisted fracture reduction. The influence of the muscle force on the robot system was predicted and managed. The simulation results provide a basis for a fracture reduction path plan that ensures patient safety and a useful reference for the mechanical design of the robot.
[Show abstract][Hide abstract] ABSTRACT: This paper proposes a strategy for a group of swarm robots to self-assemble into a single articulated(legged) structure in response to terrain difficulties during autonomous exploration. These articulated structures will have several articulated legs or backbones, so they are well suited to walk on difficult terrains like animals. There are three tasks in this strategy: exploration, self-assembly and locomotion. We propose a formation self-assembly method to improve self-assembly efficiency. At the beginning, a swarm of robots explore the environment using their sensors and decide whether to self-assemble and select a target configuration from a library to form some robotic structures to finish a task. Then, the swarm of robots will execute a self-assembling task to construct the corresponding configuration of an articulated robot. For the locomotion, with joint actuation from the connected robots, the articulated robot generates locomotive motions. Based on Sambot that are designed to unite swarm mobile and self-reconfigurable robots, we demonstrate the feasibility for a varying number of swarm robots to self-assemble into snake-like and multi-legged robotic structures. Then, the effectiveness and scalability of the strategy are discussed with two groups of experiments and it proves the formation self-assembly is more efficient in the end.
Journal of Intelligent and Robotic Systems 05/2015; DOI:10.1007/s10846-015-0235-x · 1.18 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Skid-steering mobile robots are widely used because of their simple mechanism and robustness. However, due to the complex wheel-ground interactions and the kinematic constraints, it is a challenge to understand the kinematics and dynamics of such a robotic platform. In this paper, we develop an analysis and experimental kinematic scheme for a skid-steering wheeled vehicle based-on a laser scanner sensor. The kinematics model is established based on the boundedness of the instantaneous centers of rotation (ICR) of treads on the 2D motion plane. The kinematic parameters (the ICR coefficient , the path curvature variable and robot speed ), including the effect of vehicle dynamics, are introduced to describe the kinematics model. Then, an exact but costly dynamic model is used and the simulation of this model's stationary response for the vehicle shows a qualitative relationship for the specified parameters and . Moreover, the parameters of the kinematic model are determined based-on a laser scanner localization experimental analysis method with a skid-steering robotic platform, Pioneer P3-AT. The relationship between the ICR coefficient and two physical factors is studied, i.e., the radius of the path curvature and the robot speed . An empirical function-based relationship between the ICR coefficient of the robot and the path parameters is derived. To validate the obtained results, it is empirically demonstrated that the proposed kinematics model significantly improves the dead-reckoning performance of this skid-steering robot.
[Show abstract][Hide abstract] ABSTRACT: This paper presents mechatronic design and locomotion control of a biomimetic robotic fish that swims using thunniform kinematics for fast cruising. Propulsion of the robotic fish is realized with a parallel four-bar propulsive mechanism that delivers combined translational and rotational motion to a lunate caudal fin. A central pattern generator controller, composed of two unidirectionally coupled Hopf oscillators, is employed to generate robust, smooth and coordinated oscillatory control signals for the tail joints. In order to maintain correct phase relation between joints during fast tail beating, a novel phase adjusting mechanism is proposed and incorporated into the controller. The attitude of the robotic fish in fast swimming is stabilized using an attitude and heading reference system unit and a pair of pitching pectoral fins. The maximum speed of the robotic fish can reach 2.0 m s−1, which is the fastest speed that robotic fishes have achieved. Its outstanding swimming performance presents possibilities for deployment to real-world exploration, probe and survey missions.
[Show abstract][Hide abstract] ABSTRACT: In this paper, we present a co-evolution framework of configuration and control for swarm self-assembly robots, Sambots, in changing environments. The framework can generate different patterns composed of a set of Sambot robots to adapt to the uncertainties in complex environments. Sambot robots are able to autonomously aggregate and disaggregate into a multi-robot organism. To obtain the optimal pattern for the organism, the configuration and control of locomoting co-evolve by means of genetic programming. To finish self-adaptive tasks, we imply a unified locomotion control model based on Central Pattern Generators (CPGs). In addition, taking modular assembly modes into consideration, a mixed genotype is used, which encodes the configuration and control. Specialized genetic operators are designed to maintain the evolution in the simulation environment. By using an orderly method of evaluation, we can select some resulting patterns of better performance. Simulation experiments demonstrate that the proposed system is effective and robust in simultaneously constructing the adaptive structure and locomotion pattern. The algorithmic research and application analysis bring about deeper insight into swarm intelligence and evolutionary robotics.
[Show abstract][Hide abstract] ABSTRACT: The aquatic unmanned aerial vehicle (AquaUAV), a kind of vehicle that can operate both in the air and the water, has been regarded as a new breakthrough to broaden the application scenario of UAV. Wide application prospects in military and civil field are more than bright, therefore many institutions have focused on the development of such a vehicle. However, due to the significant difference of the physical properties between the air and the water, it is rather difficult to design a fully-featured AquaUAV. Until now, majority of partially-featured AquaUAVs have been developed and used to verify the feasibility of an aquatic–aerial vehicle. In the present work, we classify the current partially-featured AquaUAV into three categories from the scope of the whole UAV field, i.e., the seaplane UAV, the submarine-launched UAV, and the submersible UAV. Then the recent advancements and common characteristics of the three kinds of AquaUAVs are reviewed in detail respectively. Then the applications of bionics in the design of AquaUAV, the transition mode between the air and the water, the morphing wing structure for air–water adaptation, and the power source and the propulsion type are summarized and discussed. The tradeoff analyses for different transition methods between the air and the water are presented. Furthermore, it indicates that applying the bionics into the design and development of the AquaUAV will be essential and significant. Finally, the significant technical challenges for the AquaUAV to change from a conception to a practical prototype are indicated.
[Show abstract][Hide abstract] ABSTRACT: Drilling end-effector is a key unit in autonomous drilling robot. The perpendicularity of the hole has an important influence on the quality of airplane assembly. Aiming at the robot drilling perpendicularity, a micro-adjusting attitude mechanism and a surface normal measurement algorithm are proposed in this paper. In the mechanism, two rounded eccentric discs are used and the small one is embedded in the big one, which makes the drill’s point static when adjusting the drill’s attitude. Thus, removal of drill’s point position after adjusting the drill attitude can be avoided. Before the micro-adjusting progress, four non-coplanar points in space are used to determine a unique sphere. The normal at the drilling point is measured by four laser ranging sensors. The adjusting angles at which the motors should be rotated to adjust attitude can be calculated by using the deviation between the normal and the drill axis. Finally, the motors will drive the two eccentric discs to achieve micro-adjusting progress. Experiments on drilling robot system and the results demonstrate that the adjusting mechanism and the algorithm for surface normal measurement are effective with high accuracy and efficiency.
创新点 (1)设计一种微型姿态调整机构, 实现对钻头姿态进行调整, 使其沿制孔点法线进行制孔, 提高孔的垂直度. 使得钻头调整前后, 钻头顶点保持不变, 提高制孔效率. (2)利用4个激光测距传感器, 根据空间不共面四点确定唯一球, 测得制孔点处的法线向量, 为钻头的姿态调整做准备.
[Show abstract][Hide abstract] ABSTRACT: In comparison with conventional shape memory actuated structures, antagonistic shape memory alloy (SMA) actuators permits a fully reversible two-way response and higher response frequency. However, excessive internal stress could adversely reduce the stroke of the actuators under repeated use. The two-way shape memory effect might further decrease the range of the recovered strain under actuation of an antagonistic SMA actuator unless additional components (e.g., spring and stopper) are added to regain the overall actuation capability. In this paper, the performance of all four possible types of SMA actuation schemes is investigated in detail with emphasis on five key properties: recovered strain, cyclic degradation, response frequency, self-sensing control accuracy, and controllable maximum output. The testing parameters are chosen based on the maximization of recovered strain. Three types of these actuators are antagonistic SMA actuators, which drive with two active SMA wires in two directions. The antagonistic SMA actuator with an additional pair of springs exhibits wider displacement range, more stable performance under reuse, and faster response, although accurate control cannot be maintained under force interference. With two additional stoppers to prevent the over stretch of the spring, the results showed that the proposed structure could achieve significant improvement on all five properties. It can be concluded that, the last type actuator scheme with additional spring and stopper provide much better applicability than the other three in most conditions. The results of the performance analysis of all four SMA actuators could provide a solid basis for the practical design of SMA actuators.
SMART STRUCTURES AND SYSTEMS 11/2014; 14(5):765-784. DOI:10.12989/sss.2014.14.5.765 · 1.37 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper presents a numerical method for parameter synthesis of a central pattern generator (CPG) network to acquire desired locomotor patterns. The CPG network is modeled as a chain of unidirectionally or bidirectionally coupled Hopf oscillators with a novel coupling scheme that eliminates the influence of afferent signals on amplitude of the oscillator. The method converts the related CPG parameters into dynamic systems that evolve as part of the CPG network dynamics. The frequency, amplitude, and phase relations of teaching signals can be encoded by the CPG network with the proposed learning rules. The ability of the method to learn instructed locomotor pattern is proven with simulations. Application of the proposed method to online gait synthesis of a robotic fish is also presented.
[Show abstract][Hide abstract] ABSTRACT: We have developed a robot system for closed diaphyseal fracture reduction. Because accuracy is essential for the treatment effects of the robot system and for the safety of both the patients and surgeons, we analysed accuracy in a systematic way. Both the structure of the robot and the operation procedure are described. Using the transfer model of errors in series and the error differential solving method for parallel mechanisms, an error model was established, and the main influencing factors of errors were considered. The Monte Carlo method was used to perform the simulation based on the error model. Experiments of image registration, of the mechanism and of the whole robot system were tested in different aspects to verify that the results of the simulation are correct. The system accuracy was compared with clinical standards to show that the robot system fulfilled the requirements for closed diaphyseal fracture reduction. The accuracy analysis method also provides an efficient path for other medical robots.
International Journal of Advanced Robotic Systems 10/2014; 11(169). DOI:10.5772/59184 · 0.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Image distortion correction and geometric calibration are critical operations for using C-arm DSA (Digital Subtraction Angiography) images to digitally navigate vascular interventional surgery. In traditional ways, C-arm images are corrected with global or local correction methods where a supposed virtual ideal image is needed, and then the corrected images are utilized to calibrate the C-arm with a pin-hole model. In this paper, we propose a new method to calibrate the C-arm with a nonlinear model and to improve navigation performance. We first calibrate the C-arm with a nonlinear model and then the distortion correction is accomplished without virtual ideal image. In this paper, the nonlinear model of C-arm imaging system is addressed at first, and then the C-arm is calibrated with a two-stage method. In the first stage, the C-arm is calibrated with the markers in image center by RAC (radial alignment constraint) method, and in the second stage the calibration parameters are optimized with Levenberg-Marquadt algorithm by minimizing the sum of the square of difference between all markers' real distorted positions and their theoretical distorted positions in the phantom image. Based on the calibration result, the image distortion can be corrected. To verify our method, experiments were conducted with a conventional DSA C-arm machine in hospital. The errors in distortion correction and 3D (three-dimensional) reconstruction were quantitatively compared with the global polynomial correction method and visual model method, and the results showed that the proposed method had better performance in distortion correction and 3D reconstruction.
Computers in Biology and Medicine 09/2014; 52. DOI:10.1016/j.compbiomed.2014.06.009 · 1.24 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper proposed hardware and software structure of the AGV system, localization method and tracking control method. In order to achieve long time and high precision localization of the AGV, this paper proposed a multi-sensor information fusion method for localization. The method was based on the characteristics of the used sensors, and adopted Kalman filter to fuse the heading direction data and position data respectively to obtain the best estimate value of AGV posture information. This paper used the control rule designed by Kanayama and the reference velocities and posture of target which were planned in advance and updated continuously for tracking control. This approach realized the tracking control accuracy and stability of the AGV. Some experiment results verified the correctness of localization method and tracking control method of the AGV system on the basis of the differential AGV.
2014 International Symposium on Computer, Consumer and Control (IS3C); 06/2014
[Show abstract][Hide abstract] ABSTRACT: A movement planning method for attitude adjustment of a drilling robot is presented in this paper. The double eccentric discs normal adjustment mechanism is used in the robot to adjust the attitude of the drill axis. To improve the adjustment efficiency, the robot should rotate the eccentric discs to the target point in a most effective way. But there are two available directions and attitudes to rotate, while the anti-trigonometric functions also have two solutions, the key problem of the movement planning is how to choose the optimal solutions from these calculated solutions to rotate the eccentric discs to improve the rotary efficiency. The principle of choosing the solutions is that the eccentric discs should rotate in the minimum absolute angle values to move to the target point. Finally, the movement loci from the initial position and a specific attitude to some different points in different quadrants are simulated in Mat lab to verify the feasibility of the rotary angle calculation method.
2014 International Symposium on Computer, Consumer and Control (IS3C); 06/2014
[Show abstract][Hide abstract] ABSTRACT: This paper presents a biomimetic robotic fish that swims using thunniform kinematics for advanced underwater mobility. Propulsion and maneuvering of the robotic fish are achieved with a lunate caudal fin that undergoes combined translational and rotational motion. A parallel four-bar propulsive mechanism attached to the rear of the rigid torpedo-shaped body is used to deliver motor rotation to the caudal fin. Oscillatory control signals for the tail joints are generated with a CPG controller composed of two unidirectionally coupled Hopf oscillators. Coupling terms that allow direct specification of phase relation between oscillators are formulated. The maximum speed of the robotic fish can reach 2.0 m/s and excellent maneuverability has been exhibited. The outstanding swimming performances present exciting possibilities for real-world deployment of the robotic fish.
Proceedings of 2014 IEEE International Conference on Robotics and Automation; 05/2014
[Show abstract][Hide abstract] ABSTRACT: Purpose ‐ The purpose of this paper is to present a Rao–Blackwellized particle filter (RBPF) approach for the visual simultaneous localization and mapping (SLAM) of small unmanned aerial vehicles (UAVs). Design/methodology/approach ‐ Measurements from inertial measurement unit, barometric altimeter and monocular camera are fused to estimate the state of the vehicle while building a feature map. In this SLAM framework, an extra factorization method is proposed to partition the vehicle model into subspaces as the internal and external states. The internal state is estimated by an extended Kalman filter (EKF). A particle filter is employed for the external state estimation and parallel EKFs are for the map management. Findings ‐ Simulation results indicate that the proposed approach is more stable and accurate than other existing marginalized particle filter-based SLAM algorithms. Experiments are also carried out to verify the effectiveness of this SLAM method by comparing with a referential global positioning system/inertial navigation system. Originality/value ‐ The main contribution of this paper is the theoretical derivation and experimental application of the Rao–Blackwellized visual SLAM algorithm with vehicle model partition for small UAVs.
[Show abstract][Hide abstract] ABSTRACT: In this study, we theoretically model and experimentally investigate the electrode electrical properties and the mechano-electrical properties of the ionic polymer-metal composite (IPMC) sensor. A physics-based model of the electrode was developed. In addition, based on the Poisson-Nernst-Planck system of equations, the current in the polymer membrane was modeled. By combining the physics of the polymer membrane and the electrode, the model of the surface electrical potential of the IPMC sensor was proposed. Experiments were conducted to test the electrical characteristics of the electrode and validate the model. The results demonstrate that the model can well describe the resistance, capacitance, and surface electrical potential of the IPMC electrode under external oscillation. Based on the model, a parametric study was done to investigate the impact of the parameters on the IPMC electrode properties. The results show that by changing the parameters of the electrode, such as the particle diameter, the electrode thickness, and microstructure, the electrical properties of the electrode can be changed accordingly. The current method of examining the electrode properties may also be applied to the study of electrodes for other smart materials.
[Show abstract][Hide abstract] ABSTRACT: In recent years, known as multi-discipline, integration, product and system, mechatronics education has drawn worldwide attention. On the foundation of 7 years’ mechatronics education experience, and taking the characteristics of Chinese undergraduate students into consideration, Beihang University improved the previous teaching mode, and formed a competition based project practice teaching mode. After one year’s exploration and practice, this mode more easily stimulates the enthusiasm and initiative of students, enhances their hands-on ability, innovative thinking and teamwork spirit. The experiment achievements and feedbacks from students prove that this mode largely realized the goal of the course.