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Designing the Second Chassis Layer of the Robot: A Deep Dive



The second chassis layer plays a vital role in the robot since it contains both low-level and high-level systems. Designing this layer requires careful consideration of various factors such as space allocation, component placement, and accessibility for maintenance purposes.


To achieve an efficient design for the second chassis layer, Solidworks was employed as a powerful 3D modeling software. Solidworks offers advanced tools and features that enable precise designing while taking into account all dimensions and specifications.

Once the design was finalized on Solidworks, it was time to bring it into reality by cutting it using a laser-cut machine.


After obtaining the laser-cut pieces, fixing the first chassis layer with the second chassis layer became the next crucial step. To fix these 2 layers, several 3D-printed shaft spacers are printed. These spacers served as supports that maintained an appropriate distance between them while allowing screws to tighten and secure the layers together. This ensured structural integrity and stability for the overall robot.


To ensure the functionality of SARA's motors and RC receiver with the microcontroller, a bench test was conducted. This test involved connecting the motors to the microcontroller and testing their responsiveness to commands from the RC receiver.


Finally, recording a video to demonstrate the achieved drive-by-wire level was an essential step in showcasing the progress of SARA. This video would provide a visual representation of how SARA moves smoothly using the RC controller.


Step 1: Designing/Cutting the Second Chassis Layer with Solidworks


Designing the second chassis layer for your SARA robot is an important step since it will contain both the Low-Level and the High-Level systems that are responsible for controlling the robot.

The image below shows the different components available on the second layer of the chassis.


Once the design of the second chassis layer for the SARA robot is complete using Solidworks, it is time to bring the design to life, the next step is to cut the design using a laser cut machine. This process ensures precision and accuracy in creating the necessary components for the robot's structure. With this step completed, we now have all the necessary components for assembling our SARA robot's chassis layer.



Step 2: Bridging the Gap, Connecting the Two Chassis Layers


To create a secure connection between the two layers, 3D-printed shaft spacers are used. These shaft spacers act as standoffs between the layers, providing a gap that allows for easy access to the components while maintaining structural stability. The dimensions of these shaft spacers should be 15 cm in length to provide sufficient space between the layers.


Once you have obtained or created the 3D-printed shaft spacers, place them at strategic points along the perimeter of the second chassis layer. These points should correspond with pre-determined mounting holes or slots on both chassis layers. Make sure to evenly distribute these shaft spacers to maintain balance and prevent any unnecessary stress on specific areas of the robot.




Step 3: Performing a Bench Test for the Motors and RC Receiver


Before the robot could be set into motion, a series of bench tests were required. These tests were crucial to ensure the functionality of the motors and the RC receiver with the microcontroller before proceeding with further integration and testing. In this step, we will discuss the importance of bench testing, provide a procedure for conducting the test, and highlight the significance of testing the microcontroller.


Bench testing is crucial as it allows the identification of any potential issues or malfunctions with the motors and RC receiver without risking damage to other components or systems. By isolating these components from the rest of the robot, we can focus solely on their performance and make any necessary adjustments or repairs before moving forward.


Firstly, we connect each motor to its respective power source using appropriate connectors or cables. We ensure that all connections are secure and properly insulated to prevent any electrical shorts or damage. The Hub motors are connected to the ODrive motor driver with the hall sensor feedback, since this motor drive is a closed-loop driver, and after initializing the motor with the corresponding parameters, we got the result shown in the video below.


Secondly, we connect the RC receiver with the microcontroller and try to read data from it. This receiver gets a PWM signal on each channel from the RC so the next step was to decode this PWM signal into integer or float values to get a range so we can control the robot accordingly.

After decoding the signals, the drive channel is converted into a range between [-1 ~1] and it represents the speed in m/s. As for the steering, it is also converted between [-1~1] and it represents the angular rotation in rad/s. Also regarding the 2 buttons they are converted into boolean values.

The image below shows the reading from the RC channels printed on the monitor.



Showcasing the Achievement: Drive by Wire Level


The term "Drive-By-Wire" (DBW) traditionally refers to automotive systems where electronic controls replace mechanical linkages. In the context of robotics, especially with SARA, the Drive-By-Wire level signifies the capability to remotely maneuver the robot using control mechanisms such as an RC controller or other advanced control interfaces


Achieving this level is not merely about remote operation. It serves as a testament to the robot's comprehensive system functionality and shows the good integration of its various subsystems. This includes the robot's sensory inputs, processing capabilities, actuator responses, and feedback mechanisms.

In essence, the achievement of the Drive-By-Wire level in SARA showcases the pinnacle of robotic design, where advanced electronics, software algorithms, and mechanical systems come together to create a cohesive and highly functional unit.




In summary, designing the second chassis layer for your SARA robot involves using Solidworks to create a precise design, cutting it using a laser cut machine, connecting it to the first chassis layer with 3D printed shaft spacers, performing bench tests for motor functionality, and recording a video to showcase its drive by wire abilities. By following these steps meticulously, you can ensure that your SARA robot is ready to navigate autonomously while displaying customized advertisements based on gender and age detection.


[2/July ~ 15/July 2023]


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