I strategically selected the component placements with a focus on optimizing the center of gravity (CG) to ensure the robot’s balance and stability. Each component was positioned to achieve a low, centralized CG, reducing the risk of tipping during movement. The LiDAR sensor is placed above the base , and the depth camera is placed at the top. The top also features a ultrasonic sensor, this is to protect the lamp, incase there are obstacles directly above the robot, out of view of the camera.
To assess the structural strength, I conducted a Finite Element Analysis (FEA) to evaluate the stress and strain distribution across the chassis. By incorporating the weight of all components—including motors, sensors, and the UVC lamp—I ensured that the chassis could withstand operational forces without failure. This analysis contributed to optimizing both the structural integrity and weight distribution, ultimately supporting stable and efficient robot performance.
| CAD files | Sourcing | Component justification |
| Battery | Mockup created by me | · 12V 15000Ah Rechargeable Lithium-Ion Battery Pack . Battery must be sufficient for continuous usage. |
| pi | Obtained from GRABCAD | · Raspberry Pi 5 Single Board Computer (8GB) Quicker Deal As the robot will be simulated on ROs , a ROs compatible micro computer is necessary, thats why Rpi was selected. |
| Lidar sensor | Obtained from GRABCAD | Lidar for high resolution room mapping |
| Camera | Obtained from GRABCAD | 3D depth camera for high resolution object distance sensing. And accurate surface detection. |
| UVC lamp | Mockup created by me | UVc lamp for disinfection. This is a vertical lamp . 75 Watts. If the lamp was too small, it would mean the robot would have to be too close to surfaces to sanitise, it would also take longer. However a lamp too large would mean larger power consumption and bigger battery requirement. However various lamps will be tested throughout the simulation |
| AC inveter 100 Watt | Mockup created by me | Inverter needed as UV-c lamps require Ac current |
| Stepper motor 17 | Obtained from GRABCAD | Stepper motor needed to raise and lower the lamp. |
| linear guides | Mockup created by me | Linear guides to move the lamp along |
| T8 Lead Screw | Mockup created by me | To screw the t5 lamp in |
| Coupling | Created by me | Part of the lamp system |
| Bearing | Created by me | For the lamp system |
| Stepper driver | Obtained from GRABCAD | To power stepper motor and encoded motors. |
| Lamp ballast | Created by me | To modulate frequency supplied to the lamp |
| Lamp holders | Created by me | To house the uvc lamp |
| Wires | Created by me | Connection of componenets |
| Button | Obtained from GRABCAD | Activation of system |
| Power Jack | Obtained from GRABCAD | Power connection cable |
| Alumiun profile bracket | Created by me | Also part of lamp system |
| bearing | Created by me | Part of |
| limit switch | Obtained from GRABCAD | to act as a homing button for the light, to stop it crashing against base of bot. |
| SCREW | Solidworks Toolbox | To screw brackets together. |
| Motor bracket | Created by me | To hold motor in place |
| 2020 PROFILE | Created by me | The 2020 Profile Bracket provides essential structural support for the robot’s frame. It ensures secure attachment of various components, like motors, sensors, and the UVC lamp. Its modular design allows for easy customization and adjustments, making it an ideal choice for a strong, versatile robot structure. |
| Caster wheel | GrabCad | Castor wheel with a high load bearing offers balance without friction or slipping |
| Motor Encoders | Grab Cad | Motor encoders needed to calculate odometry and offer much higher positional accuracy. |
| Sonar sensor | Grab Cad | To protect the lamp |
An FEA analysis was also performed on the design. While this remains a simulated experiment, the analysis serves as a precautionary measure to ensure the design’s readiness should the project progress to real-world testing.
Exploded view
Lower base view
View of top of lamp mechanism
Cross section of base
Front view of whole robot
Side view of whole robot
An FEA analysis was also performed on the design. While this remains a simulated experiment, the analysis serves as a precautionary measure to ensure the design’s readiness should the project progress to real-world testing.
The robot chassis design has been assessed for safety by comparing the maximum Von Mises stress (1.9e6 Pa) with the yield strength of ABS material.
The yield strength of ABS has been considered to be around 40 MPa (40,000,000 Pa). The maximum Von Mises stress was found to be 1.9 MPa (1.9e6 Pa).
Since the maximum Von Mises stress (1.9 MPa) is significantly lower than the yield strength of ABS (around 40 MPa), it has been concluded that the design is safe in terms of material strength. The maximum stress is well within the safe limits of the material.
The minimum Von Mises stress was found to be 0.65 MPa (6.5e2 Pa), which is also much lower than the yield strength of ABS. This indicates that parts of the chassis are under low stress, which is beneficial for the design.
Factor of Safety (FoS)
The Factor of Safety (FoS) has been calculated to ensure the design has an adequate margin of safety. The FoS is calculated as follows:
A Factor of Safety of 21.05 has been obtained, which is very high and indicates a significant margin of safety.
Deformation
The maximum displacement was found to be 4.8e-1 mm (0.48 mm), which is relatively small and within acceptable limits for a robot chassis. The maximum strain observed was 7.3e-4, which is also quite low and indicates minimal deformation under the applied loads.
