Actuators modelling

The three biomimetic actuator models mentioned above are driven in a solution. The next target of the advanced model is an actuator electrically driven in air. A mechanical hand composed of two smart gel fingers working in... 

SST=310,933,275 pressure does not effect the moment but it does the actuator model. 

Ihlefeld CM, Qu Z (2008) A dielectric electroactive polymer generator-actuator model modeling, identification, and dynamic simulation. Proc SPIE 6927 69270R... 

To facilitate the real applications of IPMCs in devices and robots, a unique systems approach is taken in Chapter 4 to look at the modeling of IPMC actuators and sensors. The presented actuation model is derived based on dynamics-governing partial differential equations and incorporates the effect of surface electrode resistance. The model, with nice scalabil-... 

Fig. 4.2 illustrates the geometric definitions of a cantilevered IPMC beam. The beam is clamped at one end (2 = 0), and is subject to an actuation voltage producing the tip displacement w t) at the other end z = L). The neutral axis of the beam is denoted by x = 0, and the upper and lower surfaces are denoted hy x = h and x = —h, respectively. We are interested in obtaining the relationships between the applied voltage and both the resulting current (impedance model) and the tip displacement (actuation model). 

As illustrated in Fig. 4.4, a cascade structure is taken for the actuation model. Here H s) represents the transfer function from the actuation voltage y(s) to the tip displacement w L, s) under the actuation-induced stress,... 

Fig. 4.4 Actuation model structure for IPMCs. Reprinted from [Chen and Tan (2008)] with permission from IEEE, Copyright 2008.

The full actuation model is represented by G s)H s). Since H s) involves non-rational functions, such as sinh(-), cosh(-), and a/, it is infinitedimensional. For practical implementation of feedback control design, however, finite-dimensional models are desirable. Simple model reduction steps can be taken to obtain finite-dimensional models for IPMC actuators, by exploiting the knowledge of physical parameters and specific properties of hyperboiic functions. In particular, based on the physical parameters of IPMCs (see Section 4.2.3), 7(s) 10, and K 10 , and we can make... 

Note that the impedance model, the actuation model, and the reduced model are all expressed in terms of fundamental physical parameters of IPMC and thus are geometrically scalable. On the other hand, the resulting models are amenable to system analysis and control design. Such physics-based, control-oriented models effectively bridge the gap between PDE-based physical models and low-order black-box models. For blackbox models, the parameters have no physical meanings and have to be re-identified empirically whenever the actuator dimensions are changed. 

Experiments have been conducted to validate the impedance and actuation models for IPMCs. The experimental setup is illustrated in Fig. 4.5. A cantilevered IPMC beam was placed in a small water tank and its tip displacement was measured with a laser displacement sensor (OADM 20I6441/S14F, Baumer Electric). The IPMC was subject to a voltage input generated from a dSPACE system (DS1104, dSPACE Inc.), and its current was measured for the validation of the impedance model. 

Experiments were further performed to validate the actuation model. The electromechanical coupling constant ao was identified to be 0.129 J/C. 

Using the electromechanical coupling, we can relate the actuation-induced stress to the charge density and evaluate the resulting deformation or force output. Further discussions on nonlinear actuation models for IPMCs along this line can be found in Chen et al. (2009). 

The actuation model obtained in Section 5.3.1 is an infinite-dimensional transfer function. All parameters in the model are already fundamental material parameters and actuator dimensions except the double-layer capacitance C and the resistance R. Scaling laws for C and R can be further derived to obtain a fully scalable model. In particular, G is proportional to the area A of polymer/electrolyte interface. The resistance R can be obtained as a function of material resistivity and dimensions using a transmission line model [Fang et al. (2008d)]. Fig. 5.5 shows the experimental verification of the scaling laws for C and R, respectively. 

We have also conducted experimental validation under dynamic inputs for both the admittance model and the full actuation model. For example. Fig. 5.7 shows the admittance spectra for two different actuator samples, with dimensions of 30 x 5 mm and 40 x 5 mm, respectively. For both... 

The model structure used for control design is obtained by reducing the full actuation model. First, the actuation bandwidth of a conjugated polymer actuator is low with respect to its first-mode natural frequency. For example, a sample of 20 x 5 x 0.17 mm has a natural frequency around... 

Tadokoro, S., Yamagami, S., Takamori, T., Oguro, K. An actuator model of ICPF for robotic applications on the basis of physicochemical hypotheses. In Proceedings of IEEE International Conference on Robotics and Automation, pp. 1340-1346 (2000)... 

Kanno, R., Tadokoro, S., Takamori, T., et al. (1995) Modeling of ICPF (ionic conducting polymer gel film) actuator - modelling of electrical characteristics. Proceedings of the IEEE International Conference on Industrial Electronics Control and Instrumentation, 913-8. 

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