Qin Y, Wan Z, Sun Y, et al. Design, fabrication and experimental analysis of a 3-D soft robotic snake. In: 2018 IEEE International Conference on Soft Robotics (RoboSoft), pp. 77–82, IEEE, 2018. Google Scholar The original contributions presented in the study are included in the article/ Supplementary Material, further inquiries can be directed to the corresponding author/s. Author Contributions Iterative Learning Control (ILC) is a method for control of periodic systems ( Moore and Xu, 2000). The serpentine locomotion of our snake robot is a good example of this, with motion stemming from the repetition of a single gait cycle across modules with a phase difference. Compared with other methods, ILC has minimal computational requirements while maintaining the dynamic behavior of the serpentine gait. Thirty sets of experiments are conducted to test the inflation and deflation performance of the modules in bending, which provides us with dynamic response information relevant for the bending waves used in the locomotion gaits. During the experiments, the soft robotic module is inflated to bend in a step response, then deflated to recover after a certain amount of time, following a square wave pattern. Figure 3 shows the mean inflation and deflation curve with the shaded region representing standard deviation between experiments. Based on these experiments, we quantify the inflation and deflation time constants as between 0.23 and 0.44 s. To fully inflate and deflate the chambers as possible, for each chamber it would take 0.46–0.88 s. Thus, we confine the gait frequency in the locomotion experiments to be no higher than 2 Hz, so that there is a reasonable chance for the actuators to be fully actuated.

During the Control of our 2D snake robot, the output of the controller is PWM signal for solenoid valves. The highest frequency of PWM signal that the solenoid valves can recognize is 60 Hz, thus the control frequency is limited to a considerably low value. In this section, experiments are conducted to compare the performance of ILC and PID controller under lower control frequency. By using the circuit diagram, set up the one LED to the breadboard and arduino. For this step, we removed the photocell sensors, so it would be easier to see the LED circuit. We recommend doing this also, it makes it easier to complete each step without previous work getting in the way of the breadboard, and eventually we wanted to reorganize the breadboard so it was configured as optimally as we could get it. Most likely, you will need to reorganize your breadboard also. Some form of power (see the section: "Powering the snake" for more info), I personally used a modified ATX power supply Scientists noticed the wriggling portions provided stability to keep the snake from tipping over. As more of the snake reached the step, its front body section would get longer and its rear section would get shorter while the middle body section remained roughly the same length, suspended vertically above the two steps.myServos[2*j+1].write(90+offset+amplitude*sin(Speed*rads+j*Wavelengths*shift+(Multiplier+1)*pi/4));

When attaching wiring to the LEDs, make sure that the wiring attaches to the long or short side of each LED. You cannot connect different sides of an LED together on the same circuit, they will not be able to turn on. Marvi H, Gong C, Gravish N, et al. Sidewinding with minimal slip: snake and robot ascent of sandy slopes. Science 2014;346:224–229. Crossref, Medline , Google Scholar This line writes to each of the 10 servos a sine wave. The base line angle is 90 degrees, the offset variable will control if the snake goes forward (offset=0) or turns left or right (offset=10 or -10), see GIF above. The sine wave outputs a value between [-1,1], this value can be scaled up by multiplying by the amplitude. for(int j=0; j<10; j++){ We found it was easiest to plan the speed controls out in a table before writing the if else statements. This was our table:

4. Iterative Learning Control

a modular system architecture comprising identical modules with integrated 3D soft actuation, valving, and electronics;

This material was based upon work supported by the National Science Foundation (NSF) under Grant Nos. IIS-1551219 and CMMI-1728412. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF. Conflict of InterestResearch in recreating locomotion via scales was done at Harvard University and demonstrated in this video. I was unable to devise a similar method to move the scales up and down on my robot and instead settled for attaching passive 3D printed scales to the underbelly. Duriez C. Control of elastic soft robots based on real-time finite element method. In: 2013 IEEE international conference on robotics and automation, pp. 3982–3987, IEEE, 2013. Crossref , Google Scholar

Attach wire into the Channel A and Channel B slots on the motor shield and attach the ends of the motors. You do not have to solder these yet, it will be easier if they are just twisted around the positive and negative tabs for easy removal in future steps. Vikas V, Cohen E, Grassi R, et al. Design and locomotion control of a soft robot using friction manipulation and motor–tendon actuation. IEEE Trans Robot 2016;32:949–959. Crossref , Google Scholar Since the servo has a range of [0,180] degrees we must ensure that the above values don't give an output below 0 or above 180. The following while loop is used to constrain the amplitude to with in these bounds. Mathematically we must satisfy this condition: |offset|+|amplitude|<=90 while(MaxAngleDisplacement>90){To add more LEDs onto same circuit, the LEDs must be set in parallel to each other, and everything else will be the same. The same code will be used in this part also because nothing has changed. Mobile robots are promising tools for emergency response. However, it is not easy for traditional rigid robots to explore narrow, complicated, unknown, or dangerous environments, especially where first responders cannot enter during search-and-rescue missions. myServos[2*j+1].write(90+offset+amplitude*sin(Speed*rads+j*Wavelengths*shift+(Multiplier+1)*pi/4)); //moves servos in horizontal plane WPI SRS-4 is a non-holonomic system with its turning angle bounded by (−α max, α max) over the sampling time.