raspberry pi

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Project Description: Electronic Power Steering (EPS) Control for Tractor Autopilot

The objective is to create an automatic steering system for a tractor using a standard automotive Electronic Power Steering system (EPS).

The concept is not to control the high-current steering motor directly. Instead, the original EPS electronic control unit is used because it is already designed to control the electric motor, manage current, and provide protection functions.

The system will electronically simulate the signal normally generated by the torque sensor on the steering shaft, making the EPS control unit operate as if a driver is turning the steering wheel.

Operating Principle

The EPS system consists of:

  • Electric steering motor;
  • Gear reduction mechanism;
  • Torque sensor on the steering shaft;
  • Original EPS control unit.

During normal operation, the torque sensor sends two analogue signals to the EPS control unit.

At the neutral position:

  • Channel A ≈ 2.5 V;
  • Channel B ≈ 2.5 V.

When the driver turns the steering wheel:

  • One channel voltage increases;
  • The other channel voltage decreases proportionally.

The EPS control unit analyses these two signals and determines:

  • Steering direction (left or right);
  • Motor assistance level;
  • Motor current required;
  • Motor rotation control.

Proposed Control System

The system will consist of two controllers:

1. Raspberry Pi — Main Control Unit

The Raspberry Pi will receive information from:

  • RTK GPS system;
  • Steering angle sensor;
  • Autopilot navigation software;
  • Tractor position and trajectory calculations.

The Raspberry Pi will calculate the required steering correction:

  • Turn left;
  • Turn right;
  • Required steering angle;
  • Required steering correction speed.

After calculation, the Raspberry Pi sends commands to the ESP32 controller.

2. ESP32 — Analogue Signal Generator

The ESP32 receives commands from the Raspberry Pi and generates two analogue signals that simulate the original torque sensor output.

Example:

Neutral position:

  • Channel A = 2.5 V;
  • Channel B = 2.5 V.

Command: Turn left

  • Channel A voltage increases;
  • Channel B voltage decreases.

Command: Turn right

  • Channel A voltage decreases;
  • Channel B voltage increases.

These two simulated signals are connected to the EPS control unit input, replacing the original torque sensor signal.

System Architecture

RTK GPS / Steering Sensors
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        Raspberry Pi
     (Autopilot algorithm)
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            ESP32
 (Analogue signal generation)
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  Simulated torque sensor signals
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       EPS Control Unit
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      Electric Steering Motor
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      Tractor Steering System

Advantages of This Approach

  • No need to design a high-current motor controller;
  • The original EPS power electronics are used;
  • Factory motor protection remains active;
  • Smooth and precise steering control;
  • Suitable for tractor autonomous steering systems.

Development Tasks

The electronics developer needs to:

  1. Connect Raspberry Pi and ESP32 communication (UART/CAN/USB).
  2. Generate two precise analogue output channels (0–5 V).
  3. Create the relationship between Raspberry Pi commands and the two sensor-simulation voltages.
  4. Implement smooth signal changes for accurate steering control.
  5. Integrate the EPS system with the tractor autopilot controller.

The final goal is to use the original automotive EPS system as an autonomous steering actuator controlled by an RTK-based tractor autopilot system.