The objective of this senior-level design course is to create a micro spider-bot that replicates a scaled down version of the spring 14’ spider-robot (six-legged). The ability of this micro spider is to walk on forest like terrain (dirt/grass), while maintaining a spider-like form controlled wirelessly through Bluetooth.
Level 1 Requirements:
Level one requirements are functional requirements, and branch out to become higher and more specific level requirements. Our level one requirements involve design guidelines, structure and kinematics, wireless interface, and safety.
Level 2 Requirements:
Level two requirements are more specific requirements. They are derived from level requirements such as expanding on level one requirements. Our level two requirements involve performance and safety.
Major Project Features:
This uSpiderbot is created to essentially be a skeleton of a spiderbot. It is created from laser cut acrylic material. Acrylic can be drilled and manipulated to fit the applied components. Due to the simplistic design of the uSpiderbot, it is easily upgradable by laser cutting desired add ons and improving the structure of the uSpiderbot.
Every body part of the uSpiderbot is created by laser cutting acrylic. The SolidWorks design will be provided on Arxterra for reproduction, as well as procedures and components used to create the uSpiderbot. This allows the uSpiderbot to be mass produced.
The uSpiderbot will have a HC-06 Bluetooth module connected, allowing wireless control through ArxRobot.
Initially when the semester began, the President had requested that we create an homage to the Spring 2014 spiderbot. These were our initial design sketches.
System Block Diagram:
Below is the system block diagram for uSpiderBot. Starting from the top with interface, we will be controlling the uSpiderbot through the Arxterra control app on an android phone. The uSpiderBot will communicate with the Arxterra app through a HC-06 a Bluetooth module. The HC-06 Bluetooth module will be connected to an Arduino Micro which will connect through a PCB designed to control 18 servos. Power will be provided by a 1200 mAH battery to sufficiently keep the servos running and the uSpiderBot moving. The manufacture engineer will handle the dimensions, materials, and structure of the uSpiderBot.
Prototype, Sketches, and Modeling:
Team uSpiderbot was able to construct a prototype uSpiderbot out of acrylic. The prototype is composed of 18 servo motors, constructed with acrylic material, and held together with screws and laser cut slots for the servo arms.
The spring 2015 uSpiderbot is designed by Gilbert Sotelo – from manufacturing. To minimize the size and weight of the uSpiderbot, it was decided that a light and thin, but strong material would be used to construct the robot. The end decision on the material build was decided to be acrylic due to several factors, acrylic is cheap, strong, and easy to laser cut. Laser cutting the parts allow for a quick output of the uSpiderbot parts. Below are Gilbert Sotelo’s earlier design considerations.
Previous generations of spiders had their fallouts ranging from broken tibias to broken coaxes. We needed to perform a stress test in order to prevent the uSpiderbot parts from breaking.
Trade off Study:
LDO vs UBEC
Due to the high voltage output of our battery rated at 6.4V, we needed to somehow lower the voltage to protect our servos flow being destroyed. We performed a trade off study on UBECs and LDOs to see which is more efficient and practical to use on our PCB.
Micro Servo Current Test:
In order to decide on a battery to use on uSpiderbot, we first needed to test the current draw on the servos at different loads.
Programming the Adafruit Servo Driver:
After the construction of our first prototype we needed a way to program the uSpiderbot to walk. We utilized 2 16 PWM output servo drivers.
In order to move the uSpiderbot, we first needed to understand how it maneuvered. The post below explains how the robotic spider walks.
In order to accomplish one of our requirements to make uSpiderbot wirelessly controlled we needed to implement a Bluetooth module. Below explains how we tested the bluetooth’s connectivity.
Interface Definitions, Fritzing, Schematics, PCB Layout:
Included in this post are the interface definitions, fritzing diagrams, schematics, and PCB layout. The interface definitions explain the connections between the components. The fritzing diagram shows how the circuit was connected in order to test the circuit before we turned it into a PCB. The schematics show visually how the components were connected.
In order to realize the final production uSpiderbot we first needed to build it in SolidWorks. Gilbert Sotelo from manufacturing was able to render the final 3D model design.
Resource Reports (Mass, Power), Updated Cost, Schedule Status:
In the post below our resource report is posted. In the resource report we show our mass and power budget. Mass budget is the accounting for every weight added onto our uSpiderbot and figuring out how to support the weight. Our power budget displays the power consumption by each of the components used on our uSpiderbot. The updated cost lists the prices of everything we had to buy to build the uSpiderbot. Finally, the schedule status shows our progress throughout the semester.
Acknowledgments: We would like to thank Tate McGeary of this semester’s uBiped for his help with integrating our code to Arxterra.