A custom-built combat robot designed for robotics competitions, featuring a high-speed spinning drum weapon and wireless control using ESP32 microcontrollers with the ESP-NOW protocol.
The robot uses a differential drive system for mobility and a BLDC-powered spinning drum weapon for attacking opponents. The control communication between the transmitter and receiver is implemented using ESP-NOW to achieve low-latency wireless control.
This robot was designed and built for a Robowars / Battlebot competition.
The entire robot was developed independently by students without external mentorship, competing against teams with significantly higher budgets and experienced mentors.
Despite these constraints, the robot performed competitively and successfully engaged in multiple battles.
This project provided valuable experience in:
- robotics system design
- embedded systems programming
- wireless communication
- power electronics
- mechanical weapon systems
- Wireless robot control using ESP32 + ESP-NOW
- Differential drive mobility system
- High-energy spinning drum weapon
- Pulley and timing belt transmission
- Dual battery architecture
- Custom joystick-based controller
- Low-latency wireless control
The robot consists of three major subsystems:
Two DC gear motors drive the robot using a differential drive configuration.
Motor control is implemented using BTS7960 high-current motor drivers, allowing forward, reverse, and turning movements.
The weapon is a horizontal spinning drum driven by a BLDC motor.
Key characteristics:
- Drum supported by welded bearings
- BLDC motor drives drum using timing belt and pulley
- Steel bolts welded onto drum act as impact teeth
- High rotational energy enables powerful hits during combat
The robot uses two ESP32 microcontrollers communicating via ESP-NOW protocol.
Advantages of ESP-NOW:
- very low latency
- reliable communication
- no WiFi router required
The handheld controller consists of:
- ESP32
- Joystick module
- Button for weapon control
The controller reads joystick input and sends movement commands wirelessly to the robot.
Control mapping:
| Input | Function |
|---|---|
| X-axis | Left / Right turning |
| Y-axis | Forward / Backward |
| Button | Toggle weapon motor |
The controller ESP32 is powered using a power bank.
The ESP32 inside the robot receives wireless commands and performs the following actions:
- Controls left and right drive motors
- Adjusts speed using PWM
- Toggles the weapon BLDC motor through ESC
The receiver also processes joystick offsets and converts them into motor speed commands.
The robot uses two independent battery systems.
Powers:
- BLDC motor
- ESC
Powers:
- ESP32 receiver
- BTS7960 motor drivers
- Drive motors
- other electronics
Buck converters (CA-1235) are used to step down voltage for electronics.
This separation prevents weapon power spikes from affecting the control electronics.
| Component | Specification | Quantity |
|---|---|---|
| Backup Chassis | Mechanical chassis | 1 |
| DC Gear Motor | 12V 200RPM Johnson Motor | 2 |
| Motor Driver | BTS7960 43A H-Bridge | 2 |
| Li-Po Battery | 11.1V 4200mAh 35C 3S | 1 |
| Brushless Motor | DYS X2812 900KV 3–6S | 1 |
| UBEC | 5V 5A Bidirectional | 1 |
| Timing Belt + Pulley | Weapon transmission | 1 |
| Bearings | Weapon rotation | 2 |
| Wheels | Drive system | 2 |
Total project cost ≈ ₹22,884
The weapon is a horizontal spinning drum.
Design characteristics:
- Drum welded with high-strength bolts
- Drum mounted on bearings
- Belt-driven from BLDC motor
- Designed to store rotational kinetic energy
The spinning drum strikes opponents with high-energy impacts.
The receiver ESP32 processes joystick data using the following logic:
- Convert joystick offsets from center
- Apply dead zone filtering
- Calculate motor speed using PWM
- Adjust left/right motor speeds for turning
- Toggle weapon motor using ESC signal
The ESC is controlled using PWM signals generated by the ESP32.
During the competition one issue occurred:
- The robot could not move properly in one direction (either reverse or turning).
Possible causes:
- motor driver wiring
- incorrect motor polarity
- logic error in motor control
Future versions will include improved testing and diagnostics.
Although the robot did not secure a podium position, it successfully competed against teams with significantly higher budgets.
Key takeaways:
- Built with limited resources
- Designed and assembled entirely by students
- Gained hands-on experience in robotics engineering
- Improved drivetrain reliability
- Weapon speed control
- Telemetry feedback
- Stronger chassis
- Better motor control algorithms
- Improved wireless failsafe mechanisms
Nisarg Vyas
B.Tech Computer Science and Engineering
IIIT Vadodara (IIITV-ICD)