Combat Robot (Gladius)

Analysis

This project utilized a lot of statics to determine the forces each part of the robot would experience during an impact which influenced the geometry of the blade, the chassis, and the truss system that supported the blade. Mechanics of materials was used equally as much to determine what material properties were needed for each section, whether that be the hard steel armor or the high strength aluminum chassis. Dynamics was used to determine the forces that the robot's weapon could output, the time it took for the weapon to spin up, and the speed of the robot.


The design requirements for this project included:


  1. The entire robot must have been less than 3 lbs.
  2. The entire robot must have been more than 2.5 lbs.
  3. The robot must have been able to drive or return to a driving state when in any orientation in less than 10 seconds.
  4. The robot must have been able to be FULLY deactivated, which includes power to drive and weaponry, in under 60 seconds by a manual disconnect.
  5. Spinning weapons must have come to a full stop within 60 seconds of the power being removed using a self-contained braking system.
  6. Cost of the project, including spare parts, must have been less than $600.
  7. Any electronic component must have been able to be fixed or replaced in less than 15 minutes.
  8. Robot’s weapon must not weigh more than 1 lb.
  9. The robot’s weapon must have a rotational moment of inertia of at least 5 lb-in2
  10. The robot’s weapon must have been able to spin up to 90% of its max speed in less than 5 seconds.
  11. The robot’s weapon must have been able to survive a force of more than 400 lb. applied tangential to the spinning weapon.
  12. The angular velocity of the robot’s weapon must reach at least 3000 RPM.
  13. The robot’s weapon must have an output energy of at least 170 J.
  14. The robot’s truss system that supports the weapon must be able to withstand at least 600 lbs. of force in the x and y directions coming from the main weapon.
  15. The bolts on the robot’s weapon insert, top and bottom plates and armor must not fail when the insert or armor experiences at least 300 lbf. along the plane of shear.
  16. The bolts and standoffs on the robot’s top and bottom plates must not fail under a tensile force of at least 300 lbf.
  17. The robot must be able to drive at a speed of at least 2.5 mph.
  18. The weapon must not deflect more than .1” at its tip when under 500 lb. of force

Robot Drive Speed

Figure A-1: Robot Drive Speed Calculation

Electronic Component Replacement Time

In combat robotics, parts get damaged and need repair or replacement. It was crucial that the robot be easy and fast to repair in the event of an electronic failure so an emphasis was made on the design of the robot to ensure that components were fast and easy to replace. The electronic component time calculation was performed to ensure that each component did not take too long to replace. It was assumed that the drive motor ESC (electronic speed controller) would be the longest part to replace so a cycle time analysis was conducted by timing how long it took for several parts of the replacement process to take and then adding those parts together in the end. This analysis did not only provide a predicted time it took to replace the component but also provided valuable data on what components took the longest and where improvements could be made. The final time to replace the drive ESC was 5.5 mins  which was far below the 15 minute requirement. The calculation can be seen below in Figure A-2.

Figure A-2: Component Replacement Time

Blade Deflection

It was expected that the spinning weapon of the robot would experience a great amount of force in all directions. One concern of note was when either another robot with a vertical spinning weapon made contact with the blade or when the blade hit a piece of hard sloped armor that the blade would deflect too much and cut into the weapon belt. To find the predicted deflection of the blade, a 500 lb. force was assumed to have been applied to the blade (which was similar force outputs compared to common combat robots) and a displacement calculation was conducted using the area moment of inertia of the weapon and the length of the weapon. The predicted deflection of the weapon was calculated to be 0.0144 in. which was far below the required 0.1 in. deflection. The calculation can be seen below in Figure A-3

Figure A-3: Displacement of Weapon Under 500 lb.

The robot speed is crucial in a number of ways including how maneuverable it can be in a fight and how much “bite” the spinning weapon can have on an opponent (the faster the robot runs into the opponent the more surface area of the blade hits that opponent). The total speed of the robot was calculated using the wheel diameter and motor RPM as can seen in figure A-1. The motor RPM was converted to rad/s and then multiplied by the wheel radius to get the linear speed of the robot, then that speed was converted from inches per second to miles per hour. The calculated motor speed came out to 6.9 mph which was well over the required speed of 2.5 mph.