This paper addresses the problem of motion planning for free-flying robots. Full state actuation is considered to allow for large displacements of the spacecraft. Motion planning is formulated as an optimization probl...
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This paper addresses the problem of motion planning for free-flying robots. Full state actuation is considered to allow for large displacements of the spacecraft. Motion planning is formulated as an optimization problem and kinematic as well as dynamic constraints are considered. The chosen optimization criteria are spacecraft actuation and final time. The proposed method allows solutions which do not require any spacecraft actuation for those end goals for which the robot motion is sufficient.
In this paper a biped locomotor, named as WL-15 (Waseda Leg 15), is analyzed in terms of stiffness characteristics. Basic models and a formulation are proposed in order to deduce the stiffness matrix as a function of ...
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For any two n-th order polynomials a(s) and b(s), the Hurwitz stability of their convex combination is necessary and sufficient for the existence of a polynomial c(s) such that c(s)/a(s) and c(s)/b(s) are both strictl...
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In this paper a biped locomotor, named as WL-15 (Waseda Leg 15), is analyzed in terms of stiffness characteristics. Basic models and a formulation are proposed in order to deduce the stiffness matrix as a function of ...
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In this paper a biped locomotor, named as WL-15 (Waseda Leg 15), is analyzed in terms of stiffness characteristics. Basic models and a formulation are proposed in order to deduce the stiffness matrix as a function of the most important design parameters of the WL-15 architecture. First numerical simulations and experimental tests are also carried out for stiffness performance estimation.
In this paper a non-linear fuzzy autopilot for ship track-keeping is presented. The proposed autopilot has four inputs (actual and desired heading, rate of change of heading and offset from the desired path) and one o...
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In this paper a non-linear fuzzy autopilot for ship track-keeping is presented. The proposed autopilot has four inputs (actual and desired heading, rate of change of heading and offset from the desired path) and one output (command rudder angle). The track-keeping problem is decomposed into two subtasks: (i) followthe desired heading, and (ii) bring the ship onto the desired path and keep tracking. Internally, the autopilot consists of two autopilots that fulfil these tasks simultaneously. The proposed control scheme has been verified using a non-linear model of a Mariner-class vessel and steering mechanism under the influence of wave and current disturbances. Results presented show how such a control strategy enables improved tracking performance.
In this paper a mouth opening and closing training robot, named WY-5 (Waseda Yamanashi version 5), is analyzed in terms of stiffness characteristics. The basic models and formulation are proposed in order to deduce th...
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In this paper a mouth opening and closing training robot, named WY-5 (Waseda Yamanashi version 5), is analyzed in terms of stiffness characteristics. The basic models and formulation are proposed in order to deduce the stiffness matrix as a function of the most important stiffness parameters of the WY-5 architecture. A numerical simulation is also presented to discuss main features of the system.
A novel dynamic vibration absorber is presented while exploring its practical implementation using piezoelectric ceramic (PZT) inertial actuators. It is referred to as active resonator absorber (ARA). The ARA is a pas...
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A novel dynamic vibration absorber is presented while exploring its practical implementation using piezoelectric ceramic (PZT) inertial actuators. It is referred to as active resonator absorber (ARA). The ARA is a passive absorber with an additional dynamic feedback compensator within the PZT actuator. Without any controller, the PZT inertial actuator becomes a passive vibration absorber due to the internal damping and stiffness properties of piezoelectric materials. Hence, it is inherently fail-safe. For active operation, the compensator parameters are designed such that a resonance condition is intentionally created within the absorber to mimic the vibratory energy from the system of concern to which it is attached. The resonance condition can be created through the appropriate design of the compensator and implemented through adjusting the external electrical voltage applied to the absorber. Because the parameters of the PZT actuators (i.e. stiffness, damping, and effective mass) are estimates, compensator designs based on these parameters would result in partial vibration suppression, when utilized in real applications. An auto-tuning method is, therefore, introduced to effectively tune the compensator parameters to improve vibration suppression quality. The effectiveness and stability of the proposed absorber is demonstrated through simulations when appended on a SDOF primary system.
An observer based control strategy is proposed for a flexible Cartesian (SCARA) Robot which is modeled as a flexible cantilever beam with a translational base support. A piezoelectric (PZT) patch actuator is bonded on...
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In redundant manipulator research community, the phenomenon called torque instability has not yet been completely characterized using unanimous agreement on its mechanism. This article shows that the behavior is indee...
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In redundant manipulator research community, the phenomenon called torque instability has not yet been completely characterized using unanimous agreement on its mechanism. This article shows that the behavior is indeed caused by incomplete compensation of null dynamics related with self-motion. This instability can be avoided by proper control with compensation of nonlinear null dynamics, and we propose a method to stabilize conventional redundancy resolution schemes extended to dynamic controls.
There have been many bilateral micro-teleoperation systems handling a small object. Historically, Lawrence[1] proposed the Transparency-Optimized Architecture and passivity theorem for stability analysis of bilateral ...
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There have been many bilateral micro-teleoperation systems handling a small object. Historically, Lawrence[1] proposed the Transparency-Optimized Architecture and passivity theorem for stability analysis of bilateral teleoperation. He claimed that unless the task(or environment) impedance contains a significant inertial behavior, passivity condition for Transparency-optimized architecture can not be satisfied. To overcome this problem, we analyze and propose a method which can satisfy passivity condition for the micro-teleoperation system handling a small inertial object based on the structures originated by Lawrence and Hashtrudi-Zaad et al.[2] and velocity-force scaling property of micro-teleoperation.
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