Abstract
The difficulty of finger robot grasping control designs is the inevitable coupling in the dynamics of finger joints and finger tips because this dynamics coupling effect lets the overall motion of the finger robots to be constrained by the object states when they are controlled to manipulate an object’s postures. Besides, from the practical implementation point of view, a stable and easy-to-implement control structure is also an important task for this topic. For solving these two design issues, an optimal hybrid control design which combines feedback linearization and nonlinear H2 control concepts for grasping design of three-joint dual finger robots is investigated in this study. This investigation makes two main contributions to the finger robot grasping control design: (1) an effective and acceptable control performance for finger robot grasping control designs under the effect of dynamics coupling is delivered and (2) a really simple nonlinear optimal control scheme is obtained.
Highlights
In the past decades, technological advances and the emergence of the digital era have led to the ubiquitous use of robots in daily life, and robots with most of them requiring a high-quality motion mechanism and a well-designed controller are demanded in various industrial and service fields such as industrial robots, humanoid robots, and wheel-type mobile robots.[1,2,3] One of these robots: the finger robot has attracted a lot of attention of researchers recently because the fundamental functionalities, such as grasping and manipulation, for various objects by finger robots are often required in a variety of environments
Published results[6,7] introduced some design concepts via using sensory motors for overcoming the drawback of the above-mentioned open-loop control designs. These results provide the possibility to construct a controller with the kinematics constraints of robot fingers and the grasped object; some strong assumptions are needed for these achievements
Suppose a bounded control commend F and a bounded regulation distance vector Y are given initially for the finger joint manipulating loop and the objective regulating loop, respectively, bounded tracking errors e1 and e2 for these two loops and a bounded regulation distance vector Y 1⁄4 1⁄2 Y1 Y2 T can be obtained continuously based on the proposed hybrid control design until the grasping process is finished; the feedback linearization-based controller F in equation (9) and the H2 control commend u in equation (45) are bounded
Summary
Technological advances and the emergence of the digital era have led to the ubiquitous use of robots in daily life, and robots with most of them requiring a high-quality motion mechanism and a well-designed controller are demanded in various industrial and service fields such as industrial robots, humanoid robots, and wheel-type mobile robots.[1,2,3] One of these robots: the finger robot has attracted a lot of attention of researchers recently because the fundamental functionalities, such as grasping and manipulation, for various objects by finger robots are often required in a variety of environments. The design objective is tracking errors between three-joint angles of the dual fingers robot and desired angles d should be proven to converge to zero optimally. The achievement of this converge implies the posture of the desired contact points Yd that can be tracked by the dual fingers robot successfully. If Pðe[2]; tÞ is found, a closed-form nonlinear H2 control law which guarantees the global stability of the fingersobject system in equations (1) and (2) as below can be obtained for the finger joint manipulating loop u. The closed-form solution of the nonlinear H2 posture tracking problem of dual finger joints can be obtained as follows u uÃ2ðe[2];
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