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Again, the code is similar to the photocell instructable. We create photocellReading variables to store the analog readings from the pins and then start the main loop. We will set the variable to the analog reading and print it out to see if it is working. We pause for 1 second, or else the reading will print out so fast we will be unable to read them. Snakebots are used in situations where their characteristics give them an advantage over their environment. These environments tend to be long and thin like pipes or highly cluttered like rubble. Thus, Snakebots are currently being developed to assist search and rescue teams. When a task requires several different obstacles to be overcome, the locomotive flexibility of SnakeBots potentially offers an advantage. [4] In Cobra’s case, most of the team’s members are undergraduates still active in the space exploration club, and they want to ready the concept for an actual moon mission. That will take a bit of work. Most of Cobra’s components are 3D-printed materials that wouldn’t survive the harsh thermal gradients at the lunar poles, where sun-baked crater rims give way to ice-cold depths near the floor. To make the system space-ready, Cobra’s components will have to be built from sturdy metals, like titanium, which can withstand dramatic temperature and pressure changes and resist corrosion. you don't need to use small ball bearings for the wheels, I just had a lot laying around. Alternatively you could use LEGO wheels or other toy wheels. Kano T, Yoshizawa R, Ishiguro A. Tegotae-based decentralised control scheme for autonomous gait transition of snake-like robots. Bioinspir Biomim 2017;12:046009. Crossref, Medline , Google Scholar
The vibration motor is added to simulate the a rattling tail on a snake. We were given our vibration motor from class, so we do not have a model number, but just like the other steps of this project, use the size motor that best fits the snake that you are building. We wanted the smallest motor possible, so that it would be able to fit on the small tail piece we were building. 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){ where u n is a control input at iteration n (which corresponds to a single period of the sinusoidal curvature wave), and k is a control gain. Since the locomotion method of the SRS-4 is a traveling sine wave, the control input u n represents the PWM duty cycle of the solenoid valves connecting each actuator chamber to the common pressure source. Our current prototype has four modules, hence, eight control inputs. e n−1 is the error between the bending angle amplitude of each module of the previous period and the desired amplitude. We found that, practically it is beneficial to keep the input pressure and gait frequency constant during locomotion, and thus, the distance from the Centroid trajectory to the left and right boundaries of the adaptive bounding box is a function of the steering offset in the gait algorithm.
The vibration motor will need to be as long as the snake itself so it will be able to rattle the tail. FIG. 7. Top-left: trajectory of the soft robotic snake CoM when locomotion frequency is 0.75 Hz. Top-middle: trajectory of the soft robotic snake CoM when locomotion frequency is 0.875 Hz. Bottom-left: trajectory of the soft robotic snake CoM when locomotion frequency is 1.00 Hz. Bottom-middle: soft robotic snake performing sidewinding locomotion on a paper surface. Right: error between simulation result and real-world experiment result related to distance traveled. To achieve sidewinding locomotion, the soft robotics modules should bend such that their end-plates (tips) move in circular paths with a desired phase delay between adjacent modules. For ease of implementation and to increase computational efficiency, we approximate this ideal circular gait and develop a hexagonal gait which can be simply implemented by binary inflation/deflation for each actuation chamber without controlling the pressure, which would be required to achieve precise circular tip trajectories. Figure 4 shows that the tip trajectory of the modules performing the hexagonal gait is tracing a deformed hexagon projected on the spherical workspace of the module.
Skorina EH, Onal CD. Soft hybrid wave spring actuators. Adv Intell Syst 2020;2:1900097. Crossref , Google Scholar In this paper, we proposed the fourth generation of WPI Soft Robotic Snake (WPI SRS-4) which is a modular soft robotic system. Each soft bending module has its own integrated local controller, solenoid valves, and curvature sensor. Together, these modules can be controlled using a master controller using a I2C serial network, creating an autonomous mobile soft robot. To improve the reliability of path following, we implemented iterative learning control (ILC) using on-board curvature sensors. In addition, we designed an adaptive bounding box motion planning algorithm, which is able to help WPI SRS find the path to navigate obstacles using curvature bounded path sections. This algorithm combines motion primitives with a simplified kinematic footprint of the WPI SRS, allowing it to simply plan achievable paths for this complex soft snake robot. We created a method for the SRS-4 to follow these predetermined paths, and experimentally analyzed their performance. Luo M, Pan Y, Skorina EH, et al. Slithering towards autonomy: a self-contained soft robotic snake platform with integrated curvature sensing. Bioinspir Biomim 2015;10:055001. Crossref, Medline , Google Scholar Solder the GND and 5V wires to a 3x7 hole perf board in the tail with a capacitor and screw terminals. The purpose of the capacitor is to remove any current draw spikes caused when starting up the servos, that can reset the Arduino Nano (if you don't have a capacitor you can probably get away without it, but it is better to be safe). Remember that the long prong of electrolytic capacitors need to be connected to the 5V line and the shorter prong to the GND line. Solder the the GND wire to the GND pin of the Nano and the 5V wire to the 5V pin. Note if you are using a different voltage, (see next section), say a Lipo battery with 7.4V, then wire the red wire to the Vin pin, NOT the 5V pin, doing so will destroy the pin.
5. Motion Planning and Trajectory Tracking
If the steps got taller and more slippery, the snake would move more slowly and wriggle their front and rear body less to maintain stability. When we replaces the wiring, we just twisted the end of the electrical piece and the wire together to connect the circuit. If you can, we recommend soldering these pieces together, it will create a stronger bond and be less likely to break. We needed to return some of our materials to the classroom, so we twisted the wiring together and wrapped each end in electrical tape to hold the bond together. In this step we will be setting up three photocell sensors, all of these will be needed to complete the snake. Two of these sensors will become directional sensors, controlling the motors. The more light either the right or left sensor will have will control how much power each of the motors will receive, controlling the speed and direction of the snake’s movement. The last sensor will become the ambient light sensor, detecting how much light is in the room. This is necessary for each of the directional sensors so they can tell how much more light is being directed at them; and it is necessary for the leds, if the room is dark, the leds will light up. FIG. 6. Top-left: trajectory of the soft robotic snake CoM when locomotion frequency is 1.50 Hz. Top-middle: trajectory of the soft robotic snake CoM when locomotion frequency is 1.75 Hz. Bottom-left: trajectory of the soft robotic snake CoM when locomotion frequency is 2.00 Hz. Bottom-middle: soft robotic snake performing lateral undulation locomotion from right side to left side in real world. Right: error between simulation result and real-world experiment result with relate to distance traveled. CoM, central of mass.
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