Current Issue : April - June Volume : 2015 Issue Number : 2 Articles : 7 Articles
Bionic quadruped robots received considerableworldwide research attention. For a quadruped robotwalkingwith steady paces on a\nflat terrain, using a camdrive controlmechanism instead of servomotors provides theoretical and practical benefits as it reduces the\nsystem weight, cost, and control complexities; thus it may be more cost beneficial for some recreational or household applications.\nThis study explores the robot step mechanism including the leg and camdrive control systems based on studying the bone structure\nand the kinematic step sequences of dog.Thedesign requirements for the camdrive robot legs have been raised, and themechanical\nprinciples of the leg operating mechanism as well as the control parameters have been analyzed. A cam drive control system was\nconstructed using three cams to control each leg. Finally, a four-leg demo robot was manufactured for experiments and it showed\nstable walking patterns on a flat floor....
This paper addresses the design of exponential tracking control using back stepping approach for voltage-based control of a flexible\njoint electrically driven robot (EFJR), to cope with the difficulty introduced by the cascade structure in EFJR dynamic model, to\ndeal with flexibility in joints, and to ensure fast tracking performance. Back stepping approach is used to ensure global asymptotic\nstability and its common algorithm is modified such that the link position and velocity errors converge to zero exponentially fast.\nIn contrast with the other back stepping controller for electrically driven flexible joint robot manipulators control problem, the\nproposed controller is robust with respect to stiffness uncertainty and allows tracking fast motions. Simulation results are presented\nfor both single link flexible joint electrically driven manipulator and 2-DOF flexible joint electrically driven robot manipulator.\nThese simulations show very satisfactory tracking performances and the superiority of the proposed controller to those performed\nin the literature using simple back stepping methodology....
Emotional robots are always the focus of artificial intelligence (AI), and intelligent control of robot facial expression is a hot research\ntopic. This paper focuses on the design of humanoid robot head, which is divided into three steps to achieve.The first step is to solve\nthe uncanny valley about humanoid robot, to find and avoid the relationship between human being and robot; the second step is\nto solve the association between human face and robot head; compared with human being and robots, we analyze the similarities\nand differences and explore the same basis and mechanisms between robot and human analyzing the Facial Action Coding System\n(FACS), which guides us to achieve humanoid expressions. On the basis of the previous two steps, the third step is to construct\na robot head; through a series of experiments we test the robot head, which could show some humanoid expressions; through\nhuman-robot interaction, we find people are surprised by the robot head expression and feel happy....
This paper develops nonholonomic motion planning strategy for three-joint underactuated manipulator, which uses only two\nactuators and can be converted into chained form. Since themanipulator was designed focusing on the control simplicity, there are\nseveral issues for motion planning, mainly including transformation singularity, path estimation, and trajectory robustness in the\npresence of initial errors, which need to be considered. Although many existing motion planning control laws for chained form\nsystem can be directly applied to themanipulator and steer it to desired configuration, coordinate transformation singularities often\nhappen. We propose two mathematical techniques to avoid the transformation singularities. Then, two evaluation indicators are\ndefined and used to estimate control precision and linear approximation capability. In the end, the initial error sensitivity matrix is\nintroduced to describe the interference sensitivity, which is called robustness. The simulation and experimental results show that\nan efficient and robust resultant path of three-joint underactuated manipulator can be successfully obtained by use of the motion\nplanning strategy we presented....
The tethered space robot (TSR) is a new\nconcept of space robot which consists of a robot platform,\nspace tether and operation robot. This paper presents a\nmulti-objective optimal trajectory planning and a\ncoordinated tracking control scheme for TSR based on\nvelocity impulse in the approaching phase. Both total\nvelocity impulse and flight time are included in this\noptimization. The non-dominated sorting genetic\nalgorithm is employed to obtain the optimal trajectory\nPareto solution using the TSR dynamic model and\noptimal trajectory planning model. The coordinated\ntracking control scheme utilizes optimal velocity impulse.\nFurthermore, the PID controller is designed in order to\ncompensate for the distance measurement errors. The PID\ncontrol force is optimized and distributed to thrusters\nand the space tether using a simulated annealing\nalgorithm. The attitude interferential torque of the space\ntether is compensated a using time-delay algorithm\nthrough reaction wheels. The simulation results show\nthat the multi-objective optimal trajectory planning\nmethod can reveal the relationships among flight time,\nfuel consumption, planar view angle and velocity\nimpulse number. This method can provide a series of\noptimal trajectory according to a number of special tasks.\nThe coordinated control scheme can significantly save\nthruster fuel for tracking the optimal trajectory, restrain\nthe attitude interferential torque produced by space\ntether and maintain the relative attitude stability of the\noperation robot....
A solution to the path following problem for under actuated autonomous vehicles in the presence of possibly large modeling\nparametric uncertainty is proposed. For a general class of vehicles moving in 2D space, we demonstrated a path following control\nlaw based on multiple variable sliding mode that yields global boundedness and convergence of the position tracking error to a small\nneighborhood and robustness to parametric modeling uncertainty.An error integration element is added into the ââ?¬Å?tanhââ?¬Â function of\nthe traditional sliding mode control.We illustrated our results in the context of the vehicle control applications that an underwater\nvehicle moves along with the desired paths in 2D space. Simulations show that the control objectives were accomplished....
For the high carrying capacity of the human-carrying walking chair robot, in this paper, 2-UPS+UP parallel mechanism is selected\nas the leg mechanism; then kinematics, work space, control, and experiment of the leg mechanism are researched in detail. Firstly,\ndesign of the whole mechanism is described and degrees of freedom of the leg mechanism are analyzed. Second, the forward\nposition, inverse position, and velocity of leg mechanism are studied. Third, based on the kinematics analysis and the structural\nconstraints, the reachable work space of 2-UPS+UP parallel mechanism is solved, and then the optimal motion work space is\nsearched in the reachable work space by choosing the condition number as the evaluation index. Fourth, according to the theory\nanalysis of the parallel leg mechanism, its control system is designed and the compound position control strategy is studied. Finally,\nin optimal motion work space, the compound position control strategy is verified by using circular track with the radius 100 mm; the\nexperiment results show that the leg mechanism moves smoothly and does not tremble obviously.Theory analysis and experiment\nresearch of the single leg mechanism provide a theoretical foundation for the control of the quadruped human-carrying walking\nchair robot....
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