Pneumatic components are rather rugged and suitable for harsh environments and therefore are an attractive alternative for mobile robots. Many robotics control algorithms require that the robot actuators be force or torque generators, so the robot controller can impose proper torque levels onto the robot joints as required by the control algorithm. While creating a torque generator using electric actuators is relatively straightforward using current feedback, there are challenges in transforming pneumatic actuators into pure force generators. This paper develops a control algorithm to convert pneumatic actuators into force generators. Because delivered work from a pneumatic actuator is product of the actuator force and the piston's displacement, the actuator force can be effectively controlled through precise measurement of the piston's displacement and robust control of the actuator's work. This paper first develops an exact model of a pneumatic system consisting of a double-acting cylinder and a servo-valve, with the goal of providing an insight into the design and control requirements for pneumatically actuated systems. Using the model, two subjects are presented in detail: 1) derivation of a control algorithm that converts a pneumatic actuator into a force generator for robotics control applications and 2) derivation of equations that can be used to design or size the power source for mobile robotic systems, where continuous source of power is unavailable. 相似文献
This paper presents a real-time fuzzy expert system to scheduling parts for a flexible manufacturing system (FMS). First, some vagueness and uncertainties in scheduling rules are indicated and then a fuzzy-logic approach is proposed to improve the system performance by considering multiple performance measures. This approach focuses on characteristics of the system's status, instead of parts, to assign priorities to the parts waiting to be processed. Secondly, a simulation model is developed and it has shown that the proposed fuzzy logic-based decision making process keeps all performance measures at a good level. The proposed approach provides a promising alternative framework in solving scheduling problems in FMSs, in contrast to traditional rules, by making use of intelligent tools. 相似文献
BACKGROUND: The purpose of our study was to determine the incidence and locations of M1 disease at presentation in patients with non-small cell lung cancer to help design appropriate preoperative imaging algorithms. METHODS: All patients with non-small cell lung cancer seen between 1991 and 1993 were identified, and records were reviewed. For patients with M1 disease, the sites of distant metastases and the methods of diagnosis were recorded. RESULTS: Of 348 patients identified, 276 (79%) had M0 disease and 72 (21%) had M1 disease. In 40 of 72 patients (56%), M1 disease was detected via chest or abdominal computed tomography (CT). Brain, bone, liver, and adrenal glands were the most common sites of metastatic disease, in decreasing order. Brain metastases often occurred as an isolated finding, although isolated liver metastases were uncommon. CONCLUSIONS: M1 disease was common at presentation, and was often detectable via chest CT. The incremental yield of abdominal CT over chest CT was very small, and therefore abdominal CT is not an effective method of screening for metastases if chest CT has been performed. 相似文献
This paper focuses on the problem of fault estimation for a class of interconnected nonlinear systems with time varying delays. In contrast to the common assumption imposed on the problem in most literature, here, there is no need for the delay rate to be less than one. Both actuator and component faults are considered within the general fault model invoked as multiplicative faults in this study. Robust adaptive observers are used to detect and estimate simultaneously the states and the parameter faults in each subsystem. The designed observers ensure a prescribed H∞ performance level for the fault estimation error, irrespective of the uncertainties which are assumed here to be the unknown interconnections between the subsystems. With the aid of H∞ performance index, the common assumption regarding the observer matching condition is no longer required. Sufficient conditions for asymptotic stability of the observers are derived via a matrix inequality approach with the aid of LyapunovKrasovskii function. Finally, a simulation example is presented to show the validity and feasibility of the proposed method.