Under-actuated

For an elastomer, the absolute strain under actuation depends on the prestrain. A more useful quantity is the relative strain under actuation ... 

Abstract A bond graph method is used to examine qualitative aspects of a class of unstable under-actuated mechanical systems. It is shown that torque actuation leads to an unstabilisable system, whereas velocity actuation gives a controllable system which has, however, a right-half plane zero. The fundamental limitations theory of feedback control when a system has a right-half plane zero and a right-half plane pole is used to evaluate the desirable physical properties of coaxially coupled inverted pendula. An experimental system which approximates such a system is used to illustrate and validate the approach. 

Keywords Bond graph Under-actuated systems Fundamental control limitations... 

A class of under-actuated systems, coaxially coupled inverted pendula, have been introduced and their qualitative properties analysed using established bond graph approaches. In particular, it is shown that torque actuation leads to an uncontrollable system, whereas angular velocity actuation gives a controllable system. 

The design of the braces was based on the maximum control force and the anticipated stiffness with the assurance that buckling will not occur under actuator actions. Circular steel tubes were used with 360 cm length, 165 mm diameter, 4.5 mm thickness and 564 kN strength. The measured stiffness of the braces is 98.4kN/mm in the x-direction and 73.8 kN/m in the y-direction. Four units of Parker, heavy-duty hydraulic cylinder series 2H-style TC (NFPA style Mx2) were selected as actuators, with the following... 

The sudden mixing of large amounts of reactants under heating, instead of cooling, caused a runaway reaction. Once the pressure reached 16 bar pressure safety devices were actuated, the temperature at that point had reached 160°C,... 

The actuating time for a quick-closing/quick-opening operation effected by the solenoid valves is 0.6 sec, and the actuating time under normal control is 5 sec for the inlet valves and 0.6 sec for the bypass valves. These actuating times apply to the full valve stroke outside the end position damping range. 

One of the most common devices for actuating a control system is the DC servomotor shown in Figure 4.13, and can operate under either armature or field control. 

Lantto, V., P. Romppainen, and S. Leppiivuori. Response Studies of Some Semiconductor Gas Sensors under Different Experimental Conditions. Sensors Actuators 15 (1988), pp.. 347-357. 

A hydraulic system must have a reserve of fluid in addition to that contained in the pumps, actuators, pipes and other components of the system. This reserve fluid must be readily available to make up losses of fluid from the system, to make up for compression of fluid under pressure, and to compensate for the loss of volume as the fluid cools. This extra fluid is contained in a tank usually called a reservoir. A reservoir may sometimes be referred to as a sump tank, service tank, operating tank, supply tank or base tank. 

The substitution of the two-sided tape with a film of an ionic conductor gives (Fig. 24) a triple-layered muscle working in air.114 The tape now acts as a solid electrolyte. Nevertheless, the system only works if the relative humidity in air surpasses 60%. Under these conditions, movements and rates similar to those shown by a triple layer working in aqueous solution were obtained. This device was developed in cooperation with Dr. M. A. De Paoli from the Campinnas University (Campinnas, Brazil). At the moment several groups are developing actuators, muscles, and electrochemomechanical devices based on bilayer or multilayer structures.115-125... 

The only 3D mapping system with LGSs under constmction today is that for the Gemini South 8m telescope at Cerro Pachon, Chile (Lllerbroek et al., 2002). It consists of 5 LGSs, 3 deformable mirrors with a total of 769 actuators and one 1020 subapertures wavefront sensor per LGS (Fig. 11). It is expected to be the most performing MCAO device. 

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