The quadruped robot's design is inspired by Boston Dynamics' Spot robot, which looks somewhat like a dog. It's designed for additive manufacturing and is easy to print with any commercial FDM/FFF 3D printer. While I plan to build the robot myself, this tutorial will only cover the design phase, and I will soon publish a step-by-step guide to building the quadruped robot in another post.
In this article, I will introduce you to the general design process of this robot, so you don't have to copy what I'm building. By using this tutorial, you can unleash your creativity to create any legged robot you like.
We hope you enjoy reading this article and will share your designs in the comments.
Software and equipment:
1. SolidWorks (Design)
2. Visualize (Rendering)
3. Desktop computers/laptops
4. Computer mouse (not essential, but recommended as it will make this project easier to complete.)
Step 1: Sketching Concept
Figure 1
The first step in the design process is to take out your sketchbook and begin sketching different concepts of the robot. The sketches themselves don't need to be perfect; just have a general shape and form components with roughly estimated dimensions. As shown in Figure 1 above, I started with very basic 2D sketches, depicting the robot's basic outline and limb dimensions. After developing an initial concept, I finally completed the design of this dog-inspired robot, featuring a parallel drive mechanism in its lower legs. Next, I began sketching more details, such as the placement of electronic devices, the kinematics of the legs, and the leg drive mechanism, etc. I've also shown some sketches used to develop detailed component designs.
Regarding the depiction of details, I recommend drawing the sketches in 3D for better visualization of the design. Here are some resources for product design sketching:
TheSketchMonkey's “3 Important SketchingExercises for Any Designer (Beginner) – YouTube“
https://www.youtube.com/watch?v=IM_zvACz2og&t=12s
Sketch a Day's “Sketch-A-Day – How to sketch complex organic shapes – YouTube“
https://www.youtube.com/watch?v=_JK73WLM3xQ
Reid Schlegel's “Sketching Basics 2: Perspective is King – YouTube“
https://www.youtube.com/watch?v=JK0qlnnG1WA
In addition to detailed 3D sketches, I also encourage you to draw rough sketches of components to develop better ideas.
Step 2: Import/Download Electronic Components
Considering electronic components is a crucial part of any robot design process, but designing each component individually would be tedious. Therefore, I source most of my electronic components from GrabCAD. Solidworks allows users to directly import pre-designed electronic components, such as servo motors, batteries, and controllers, into .STEP, .SLDPRT, and .STL file types for assembly; for unsupported file types, any free online converter can be used to convert the files to .STEP or .SLDPRT.
https://grabcad.com/library
Below is a list of electronic components I imported from GrabCAD:
Servo Motor: Lewansoul LX-16A bus servo | 3D CAD Model Library | GrabCAD
https://grabcad.com/library/lewansoul-lx-16a-bus-servo-1
DC-DC Buck Converter: DROK AdjustableDC Buck Converter Model 180078/180080 with built-in mount | 3D CAD ModelLibrary | GrabCAD
https://grabcad.com/library/drok-adjustable-dc-buck-converter-model-180078-180080-with-built-in-mount-1
Servo Bus Connector: LewanSoul LX-16A Servo Bus Linker | 3D CAD Model Library | GrabCAD
https://grabcad.com/library/lewansoul-lx-16a-servo-bus-linker-1
Battery: TalentCell Rechargeable 12V 3000mAh Lithium Ion Battery Pack | 3DCAD Model Library | GrabCAD
https://grabcad.com/library/talentcell-rechargeable-12v-3000mah-lithium-ion-battery-pack-1
I couldn't find a CAD file for Libre Computer (Le Potato) online, so I designed one myself: AML-S905X-CC (Le Potato) | 3D CAD Model Library | GrabCAD
https://grabcad.com/library/aml-s905x-cc-le-potato-1
Step 3: Design the thighs
Now that we have all the design materials ready, let’s start designing the quadruped robot.
Figure 2
As shown in Figure 2, to design the thigh, I started with a basic sketch. The sketch was stretched to a thickness of 30 mm. Next, I stretched the interface of the main motor shaft and created screw holes for eight M2 machine screws to install the motor connector, which is the connection interface between the motor shaft and the thigh. After completing the basic shape of the thigh, I cut out 45 x 18 mm slots for the auxiliary motor; and 50 x 18 mm slots for the lower leg. Then, other finer details were added to our CAD model, such as slots designed for line management, the auxiliary motor bracket, and related finishing touches.
Step 4: Design the calf
To design the lower leg, I followed a similar process. First, I created a basic sketch, inspired by the rough concept sketch mentioned in the first step. Then, I stretched the sketch and added more detailed elements, such as slots for the parallel linkage mechanism and modular toe cutouts.
Step 5: Assemble the legs
Figure 3
In this step, we will assemble the thigh and lower leg we just designed, and motor #2 will be fixed to the thigh (Figure 3). For this, we need to activate these three components in the work area and assemble them according to the design. Once the thigh, lower leg, and motor are assembled, the compliant linkage and Servo horn will be modeled and added to the components. At this point, the leg design is complete! Let's move on to the base design.
Step 6: Assemble the base
In this step, we will assemble all the components of the robot's base, including the electronic components and power supply.
Step 7: Assemble the legs, base, and shell to complete the design of the quadruped robot.
Once all the components were in place, we assembled them, and the design of the quadruped robot was complete! I used the Visualize software to generate high-quality renderings and finish the quadruped robot.
