PURPOSE OF PROJECT
The CSULB Hexapod project will offer an opportunity to study the limitations of a robot over a realistic terrain. A hexapod robot offers increased maneuverability and improved stability over traditional rovers. Its low center of gravity allows the robot to move over terrain that might limit a tracked or wheeled rover. Its six legged jointed design will allow the robot to change height permitting it to overcome taller obstacles that would otherwise obstruct its path. Its integration with an Android phone and open-sourced control boards allows for future builders to easily recreate or improve on the Hexapod design.
EXECUTIVE SUMMARY OF PROJECT
MAJOR PROJECT FEATURES
User Interface Control
The Hexapod will house the Android home and run the Arxterra app to provide telepresence to the user through the Arxterra Control Panel.
The Hexapod will be small enough to be easily transported. It will be easy to travel with the Hexapod and to display its features at any venue.
The final build will be controlled wireless over a Wifi connection. It will be easy to control the hexapod from any laptop over an internet connection allowing for people to connect and interact with the Hexapod from anywhere in the world.
The body of the Hexapod will be molded from a durable resin. The material can be drilled, mounted and can support a large amount of weight. The body will be easily assembled and disassembled for future upgrades or to easily replace any broken parts.
Easily Mass Produced
The resin body parts will be made from silicon molds. The molds will allow for the body parts to be easily poured and easily copied. With the documentation of the build, along with the open source code, it will be easy for anyone to build the Hexapod of their very own.
System Block Diagram
Our current estimate for the Hexapod is $600. This gives us a large margin to account for miscellaneous items such as leads, soldering equipment, cables or items that might need replacing. We are also leaving the option open to replace our current servos with higher quality servos, or to opt for a better battery if needed.
Project requirements are set by Project Manager-Ramon Luquin and will consists of the most important goals for the Hexapod.
Level 2 requirements are a reaction to the level 1 requirements and incorporate knowledge acquired as the build develops. Level 2 requirements are more project specific and will lead to our resource reports. Goals for the power requirements, materials of the build and power train will be addressed here.
LEVEL 3 SUBSYSTEM REQUIREMENTS
Level 3 requirements will be more component specific and will react to the level 2 requirements. What the characteristics of an ideal servo are will be address in this section.
Here is a detailed description of the interactions between our systems. This section has our Fritzing Diagram, Eagle Schematic Layout and our System Interface Spreadsheet.
A number of aspects are pivotal to the success of the Hexapod. Given that servos have a limited torque, and the Hexapod will be running off a battery, we will have to budget both the weight of the build and the amount of current available for all the on board electronics.
A detailed MS. Project file: HEXAPODScheduleVersion2 is available which will illustrate a detailed schedule for the tasks completed and pending. Below is an outline of the tasks that have been designated to test the different aspects of the design. At this blog we will also have a flow chart of the tasks completed and still to be completed for the build.
TRADE OFF STUDIES
These trade off studies have given us insight into some of the components that are perfect for our build, as well as eliminated components or strategies that we might have thought adequate at the beginning of our design process.
SERVO VS STEPPER MOTOR
We have tested a number of servos and stepper motors to analyze the response of each and observed their power characteristics.
HEAVY LOAD UNDER VARYING ANGLES SERVO TESTS
David Gonsalez, our Power Division Engineer, working together with Sokleng Heng, Power Division Engineer from project BiPed, designed and executed a test to calculate the current drawn from heavier loads and at different angles and with a new servo, the PowerHD 1501MG. The entire in depth test can be found at BiPed’s page. The findings from this test directly affected our decision on the servos. Up until this point, we had decided on the TowerPro MG995 as our servos. The PowerHD1501 was a great find by BiPed and after their tests, it was obvious that the servo was perfect for us as well.
As of this post, we have narrowed down the battery choices between a Venom 20C 5000mAh 7.4 LiPO battery and a Tenergy 7.4V 900mAh 25C LiPo. This pending study will define which battery choice we will make.
Since our team’s level 1 requirement is speed, the tripod gait will be the main gait used during the Hexapod’s missions.
SERVO AND STEPPER CHARACTERISTICS
David Gonsalez, Power and Computer Division Manager, conducted servo tests on the MG995. It had been decided until David conducted a new set of tests on the PowerHD1501 MG that the TowerProMG995 would be our chosen servo. The servo had met all the requirement for out buildings. When David conducted new tests along with project BiPed on a new servo, we decided that the $2 difference in servo was justifiable for the improvement in response the PowerHD offered.
MATERIAL AND FABRICATION
A material study was conducted by manufacturing engineer Daniel Berg to decide on the best materials to use for our build. Daniel looked at making the body out of aluminum, balsa wood and resin.
Daniel Berg, Manufacturing Engineer for Hexapod, has created a full 3D model of the servos, legs and femurs. It allows to have an accurate representation of the size of the model and where and how will fit all the on board electronics.
David Gonsalez, our Power Division Engineer, built a full size hexapod made out of chop sticks. He has crowned it Chop Suey. Chop Suey allows us to quickly try out some of the ideas we have and to test out code and the capabilities.
Analysis of Multi-Legged Animal + Robot Gaits. (2013, 10 23). Retrieved from Oricom Technologies: http://www.oricomtech.com/projects/leg-time.htm
Berg, D. (2013, 10 22). 3D Model. Retrieved from www.Arxterra.com: https://www.arxterra.com/3d-model/
Do, A. T. (2013, 10 24). Hexapod Gait Descriptions. Retrieved from https://www.arxterra.com/hexapod-gait-description/: https://www.arxterra.com/hexapod-gait-description/
Gonzales, D. (2013, 9 27). Hexapod Weekly Update 1. Retrieved from www.Arxterra.com: https://www.arxterra.com/hexapod-weekly-update-1/
Heng, S. (2013, 10 24). Arxterra. Retrieved from Thorough Servo Testing: https://www.arxterra.com/thorough-servo-testing/
Rawashdeh, D. N. (2013, 10 23). Retrieved from German Jordanian University: http://www.gju.edu.jo/admin/s38files/Hexapod%20Robot_%20Tariq%20Mamkegh.pdf
The following table summarizes the documents referenced in this document.
Document Name and Version
Hexapod Project ScheduleVersion 2.0
Schedule Plan for Project
Dropbox:Public Ramon Luquin/HexapodScheduleVersion2.mpp
Hexapod Project PlanVerision2
This Document in PDF format
Dropbox:Public Ramon Luquin/HexapodProjectPlanVersion2.pdf