Avoidance Control Law Research Articles

Multi-Fingered Bimanual Haptic Interface Robot with Three-Directional Force Display

This paper introduces a bimanual haptic interface robot and presents results from its trial operation. Our aim in developing a bimanual haptic interface is to display high-precision three-directional forces at all 10 fingertips of both hands of the operator. By installing two five-fingered robot hands and two robot arms, we construct a bimanual haptic interface. A haptic interface that consists of robot hands and robot arms can provide multi-point contact between the operator and a virtual environment. However, there is the risk that robot hands and robot arms will collide while an operator is manipulating the haptic interface. To solve this problem, we also propose a collision avoidance control law for the multi-fingered bimanual haptic interface. Finally, to determine the validity of the proposed interface, we carry out several experiments. These results show the validity and great potential of the proposed bimanual haptic interface.

Cooperative Avoidance Control for Multiagent Systems

The objective of this paper is to present a methodology for designing cooperative control laws for individual agents that guarantee collision avoidance in multiagent systems. The proposed avoidance control laws are easy to design and implement, and may be directly appended to the optimal control laws of the individual agents within the cooperation framework. The avoidance control laws are computed using value functions that resemble the behavior of barrier functions in the static optimization theory. The most attractive feature of the proposed optimization scheme is the fact that the avoidance laws are active only in the bounded sensing regions of each individual agent, and they do not interfere with the agents’ individual optimal control laws outside of these regions.

Three-Dimensional Collision Avoidance Control Law for Aircraft Using Risk Function and Fuzzy Logic

This paper proposes a new collision avoidance control law for aircraft. RCPA (Range of Closest Point of Approach), representing risk in the future, and TCPA (Time to CPA), representing current risk, are used as risk functions. Furthermore, fuzzy logic is introduced in order to achieve human maneuvering and to settle singular point and chattering problems that are discussed in previous studies. Avoidance strategy consists of four main phases, maintaining course, avoidance, parallel flight and recovery phase, and three transition phases. The parallel flight phase and three transition phases are introduced to achieve moderate avoidance and smooth phase transition, respectively. Simulation results show that the proposed control law settles the past problems and achieves smooth and adequate avoidance. This paper also discusses the fuzzy evaluation method.

危険度とファジィを用いた航空機の３次元衝突回避制御則

危険度とファジィを用いた航空機の３次元衝突回避制御則

Preferred gimbal angles for single gimbal control moment gyros

This paper deals with torque command generation using single gimbal control moment gyros. The angular momentum and torque envelopes are assumed to be known a priori. A method based on back integration of the gyro torque equation from desired final conditions is used to determine a family of initial gimbal angles that avoid singularities. Each member of this family is defined as a preferred initial gimbal angle set. The pseudoin- verse steering law is used during the numerical integrations. This procedure is demonstrated by means of numerical examples that include attitude control and momentum management of the Space Station Freedom. A feedback control scheme based on null motion is also developed to position the gimbals at preferred angles. ONTROL moment gyros (CMGs) are attractive space- craft attitude-control devices. They require no expendable propellant, which is a limited resource and can contaminate the spacecraft environment. Their fixed rotor speeds minimize structural dynamic excitations. They can be used for rapid slewing maneuvers and precision pointing. For low Earth or- biting spacecraft, momentum dumping can be easily achieved by gravity-gradient torques. From the steering-law viewpoint, it is widely accepted that double-gimbal CMGs (DCMGs) are preferable to single-gimbal CMGs (SCMGs). For DCMGs, steering laws proposed by Kennel 1'2 have been well accepted. The SCMGs have the advantages of possessing relative me- chanical simplicity and producing amplified torques (for low spacecraft angular velocities) on the spacecraft. However, de- velopment of gimbal steering laws for their use is made diffi- cult by the existence of internal singular states. For any system of n CMGs and any direction in space, there exist 2 sets of gimbal angles3 for which no torque can be produced in that direction, and these sets are called internal singularities. Exter- nal singular states correspond to directional angular momen- tum saturation. DCMGs have internal singularities also, but they are easier to avoid. Margulies and Aubrun3 present a geometric theory of SCMG systems. They characterize the momentum envelope of a cluster of SCMGs and identify the internal singular states. Yoshikawa4 presents a steering law for a roof-type configura- tion with four SCMGs. His steering law is based on making all of the internal singular states unstable by providing two jumps with hystereses around the singularities. Cornick5 develops singularity avoidance control laws for the pyramid configura- tion. His technique is based on the ability to calculate the instantaneous locations of all singularities. Hefner and McKenzie6 develop a technique for maximizing the minimum torque capability of a cluster of SCMGs in the pyramid con- figuration. Bauer7 concludes that it is impossible to avoid some singularities and, in general, no global singularity-avoid- ance steering law can exist. Consequently, there will be in- stances when torque demand cannot be met exactly.