How to build a replica of the TARS robot from Interstellar

9 min readJul 16, 2024

A developer named Charles Diaz has created a fully functional replica of TARS using a Raspberry Pi. This isn’t just a static model — it can move forward and turn sideways.

Charles Diaz has spent the past two years working on creating a mini replica of the TARS robot from the movie, with the goal of making it walk like TARS in the movie. The project has evolved from a functional but unreliable proof-of-concept model to a more complete and highly reliable prototype. The latest version even comes with dual robotic arms that can interact with its surroundings.

A Raspberry Pi 3B+ is used as the main control, equipped with four high-torque metal gear servo motors to drive the legs, Adafruit PCA-9685 servo driver controls the servo motors, and the power supply uses two sets of 8 NiMH batteries. It is controlled by a 5-inch HDMI display and an 8BitDo Zero 2 Bluetooth controller.

Basic walking : TARS V1 is able to achieve basic walking movements. Four high-torque metal gear servo motors drive the rotation of the two legs and the up and down movement of the body, thus simulating the gait of TARS in the movie.
Gait control : Use Raspberry Pi 3B+ as the main control, cooperate with Adafruit PCA-9685 servo driver, and write a gait control program to achieve precise control of the servo motor.
Bluetooth remote control : TARS V1 is equipped with an 8BitDo Zero 2 Bluetooth controller, and users can remotely control TARS’s walking and other movements via Bluetooth.
Display Information : The 5-inch HDMI display can display control information and status, allowing users to monitor and operate TARS in real time.
Battery power supply : TARS V1 uses two sets of 8 NiMH battery packs connected in parallel to provide sufficient power support for servo motors and other components.
Main power supply : Raspberry Pi 3B+ is powered by a 5V USB mobile phone charger to ensure stable operation of the system.

Main features:

High degree of simulation : The appearance and walking movements of TARS in the movie are restored as much as possible, making it highly realistic.
Flexibility : The modular design makes TARS V1 structurally flexible, facilitating subsequent improvements and upgrades.
Remote control : Through the Bluetooth controller, users can easily operate TARS remotely to achieve more interactive functions.

Charles Diaz published the tutorial, hardware and code on Hackster.io…

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TARS V1 production process in detail

Hardware Components

Main control computer : Raspberry Pi 3B+, running Raspbian operating system
Servo motors : Four high-torque metal gear servo motors (all installed in the fuselage), respectively controlling the rotation of the two legs and the up and down movement of the fuselage
Servo Driver : Adafruit PCA-9685 16-channel PWM Servo Driver
Power supply : Two sets of 8 (7.2V) NiMH battery packs connected in parallel
Monitor : 5-inch HDMI monitor
Remote controller : 8BitDo Zero 2 Bluetooth controller

Mechanical design

Chassis : An extruded aluminum “spine” is used as the base structure, with 3D-printed polycarbonate parts installed that form the overall drive system of TARS.
Housing : Using an aluminum sheet as the housing with a polycarbonate screen protector on top, although the aluminum material is not like the steel in the movies, it still gives the V1 a certain cinematic authenticity.
Battery and weight distribution : All heavy components are installed inside the body. Excessive battery weight makes steps heavy and affects walking effect.

Detailed production process introduction

1. Hardware Component Preparation

Before you start, you need to prepare the following hardware components:

Raspberry Pi 3B+
High torque metal gear servo motors (4 pcs)
Adafruit PCA-9685 16-Channel PWM Servo Driver
8BitDo Zero 2 Bluetooth Controller
Two 8-cell NiMH battery packs
5-inch HDMI monitor
Aluminum extrusion materials and 3D printed polycarbonate parts

2. Chassis and mechanical structure assembly

2.1 Chassis design and assembly :

The “spine” made of extruded aluminum alloy is used as the basic structure of TARS. The aluminum alloy material ensures the strength and stability of the chassis.
Polycarbonate parts are manufactured using 3D printing technology and will be installed on the “spine” to form the overall drive system of TARS.

2.2 Install the servo motor :

Four high-torque metal gear servo motors are installed inside the TARS body. Two of the servo motors are used to control the rotation of the two legs, and the other two servo motors are used to control the up and down movement of the body.
The servo motor is fixed on the aluminum alloy structure to ensure its stability and accuracy.

2.3 Housing and protective cover installation :

Aluminum plates are used as the outer shell of TARS to provide protection for internal components.
A polycarbonate screen guard is installed on top to protect the display and increase the overall aesthetics.

3. Power Management and Connections

3.1 Battery connection and wiring :

Connect two 8-cell (7.2V) NiMH battery packs in parallel to provide power to the servo motor and other components via wires. Make sure the connections are secure to avoid power failure.
Use a 12V to 6V DC step-down converter to ensure that the servo motor receives a stable power supply.

3.2 Raspberry Pi power supply :

Power the Raspberry Pi 3B+ via a 5V USB mobile phone charger to ensure stable operation of the system.

4. Electronic Control and Programming

4.1 Servo drive connection :

Connect the Adafruit PCA-9685 servo driver to the Raspberry Pi 3B+ to control the servo motor. Make sure the driver is properly connected to the servo motor and the Raspberry Pi.

4.2 Display installation and connection :

Install a 5-inch HDMI display and connect it to the Raspberry Pi via an HDMI cable to display control information and status.

4.3 Remote control configuration :

Configure the 8BitDo Zero 2 Bluetooth controller to enable it to communicate with the Raspberry Pi and remotely control the walking and other actions of TARS.

5. Software Development and Testing

5.1 Raspberry Pi system configuration :

Install the Raspbian operating system on the Raspberry Pi 3B+ and ensure that the system runs normally.

5.2 Gait control program writing :

Write a gait control program to control the rotation and movement of the servo motor through the Adafruit PCA-9685 servo driver. The program needs to consider the smoothness and accuracy of the gait to ensure that TARS can walk normally.

5.3 Debugging and Optimization :

Through multiple tests, the gait control program was adjusted and the servo motor action was optimized. The walking effect of TARS was observed, problems were recorded and adjusted.
Adjust the weight distribution to minimize the impact of your steps and avoid damage to the 3D printed drive components.

6. Final testing and improvement

6.1 Comprehensive test :

Perform a comprehensive functional test on TARS to ensure all components and control systems are functioning properly.
TARS was remotely controlled via a Bluetooth controller to test its walking and interactive functions.

6.2 Problem record and improvement :

Record problems encountered during testing, analyze causes and propose improvement plans.
Based on the test results, the mechanical structure, power management and gait control program are adjusted and optimized.

6.3 Iterative improvements :

Through multiple iterations, the design and function of TARS have been continuously improved. The weight distribution has been optimized, lightweight LiPo batteries have been used, and the gait control program has been improved to enhance the stability and endurance of TARS.

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Problems encountered during the production of TARS V1 and improvement solutions

1. Problem: Uneven weight distribution

Description : Due to the use of two sets of 8 NiMH batteries, the overall weight is relatively large, especially the heavy components are concentrated inside the fuselage, which makes the TARS V1 walk heavy and affects the smoothness and stability of walking.

improve proposals :

Switch to lightweight batteries : Replace NiMH batteries with LiPo batteries of comparable capacity but lighter. LiPo batteries are lighter and have a higher energy density, which helps reduce overall weight and improve battery life.
Optimize weight distribution : Redesign the layout of internal components to distribute the weight more evenly throughout the robot structure, avoiding the center of gravity being too high or too concentrated in one part.

2. Problem: Incomplete gait control program

Description : The initial gait control program caused TARS V1 to have heavy and violent steps, resulting in frequent damage to the 3D printed drive components, affecting the stability and durability of the robot.

improve proposals :

Optimize gait algorithm : Conduct in-depth research on the gait control algorithm, optimize the movement and coordination of the servo motor, ensure that the force and speed of each step are reasonably controlled, and reduce the impact force on the components.
Use sensor feedback : Install sensors (such as accelerometers and gyroscopes) on TARS V1 to monitor the robot’s posture and motion status in real time, adjust the gait program based on the feedback, and improve walking stability.

3. Problem: Imperfect power management

Description : Two sets of NiMH batteries are connected in parallel to provide sufficient power, but due to the type of batteries and the way they are connected, the power supply is unstable, which affects the continuous operation of the robot.

improve proposals :

Switch to a stable power source : Switching to LiPo batteries not only reduces weight but also provides a more stable power supply. Use a high-quality battery management system (BMS) to ensure the safety and reliability of battery use.
Increase power redundancy : Design a dual power system to ensure that when one set of batteries is exhausted, the other set of batteries can seamlessly switch to ensure continuous operation of the robot.

4. Problem: Durability of mechanical structure

Description : 3D printed polycarbonate parts are subject to large impact forces when the robot walks, resulting in frequent damage, affecting the durability and stability of the overall structure.

improve proposals :

Improve material selection : Choose stronger and more durable materials to replace some 3D printed parts, such as using metal or high-strength composite materials to manufacture key load-bearing components.
Structural reinforcement design : Add reinforcement ribs and support structures to mechanical design to improve the impact resistance and durability of parts.

5. Issue: Bluetooth control range and stability

Description : Using the 8BitDo Zero 2 Bluetooth controller may cause unstable signal or control delay issues under certain distance and obstacle conditions.

improve proposals :

Improve communication methods : Consider using more stable wireless communication methods, such as WiFi or ZigBee, to improve the range and stability of control signals.
Add antennas and signal amplifiers : Add an external antenna or signal amplifier to the Bluetooth module to improve communication distance and signal stability.

Future Improvement Directions

Improved gait control program : Continuously optimize the gait control algorithm, introduce machine learning technology, continuously adjust and optimize the gait based on sensor feedback, and improve the intelligence and adaptability of walking.
Improve interactive functions : Add robotic arms and more sensors to enhance TARS’s ability to interact with the environment, giving it more functions and application scenarios.
Enhanced durability : Further optimization in material and structural design ensures that the robot can operate stably in various environments and extend its service life.
Optimize energy management : Introduce solar cells or other renewable energy solutions to improve the robot’s endurance and environmental performance.

Original text and CAD drawing part code acquisition: https://www.hackster.io/charlesdiaz/how-to-build-your-own-replica-of-tars-from-interstellar-224833#cad