2. Soft robots have attracted a lot of attention in the last 10 years. For example, Professor Chris Rahn of Penn State University developed a soft robot, called OctArm, to mimic an elephant trunk or an octopus arm. The basic principle is to use a fluid system to pump fluid through composite tubes. The fluid inertance, resistance, and capacitance will couple with axial and bending stiffnesses of the composite tubes to move the tubes like elephant trunks Figure 3 shows a very primitive model to explain the interaction of the fluid system and the composite tube. The fluid system consists of a through-variable source (with prescribed flow rate Qs(t)), a long pipe (with inertance I and resistance R), an accumulator (modeled as a tank with capacitance C), and a hydraulic cylinder with area A. The composite tube is modeled as a translational domain, consisting of two masses (mi and m2), two springs (with spring constants ki and k2), a damper (with viscous damping coefficient B2), and a prescribed input load Fs (t) (e.g., the load that the soft robot needs to pick up). Note that the hydraulic cylinder couples the fluid and translational domains via elemental equations p- F/A where p and Q are the pressure and flow rate of the fluid domain, whereas F and v are the force and velocity of the translational domain. Figure 4 shows the linear graph of the soft robot model shown in Fig. 3. Answer the following questions (a) Draw the normal tree (b) Identify primary, secondary, and state variables. Identify dependent energy storage elements if there is any (c) Derive the state equation using the normal trece Q.(t) Q.(t) Figure 3: A simple model of a soft robot Figure 4: Linear graph of the soft robot