https://github.com/mataruzz/ros2_servo_motion
Micro-servo S90 ROS2 hardware interface for RaspberryPi 3B+.
https://github.com/mataruzz/ros2_servo_motion
guide hardware-interface raspberry-pi-3 ros2 servo-motor ubuntu-server
Last synced: 3 months ago
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Micro-servo S90 ROS2 hardware interface for RaspberryPi 3B+.
- Host: GitHub
- URL: https://github.com/mataruzz/ros2_servo_motion
- Owner: mataruzz
- Created: 2023-07-29T09:25:29.000Z (about 2 years ago)
- Default Branch: humble
- Last Pushed: 2023-10-29T12:47:48.000Z (almost 2 years ago)
- Last Synced: 2025-04-13T10:44:34.981Z (6 months ago)
- Topics: guide, hardware-interface, raspberry-pi-3, ros2, servo-motor, ubuntu-server
- Language: C++
- Homepage:
- Size: 37.3 MB
- Stars: 5
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# Micro-servo S90 hardware interface for RaspberryPi 3B+
The micro-servo S90 is a small, lightweight motorized device commonly used with Raspberry Pi or Arduino boards to control the precise movement of mechanical parts. It is compact, low-cost, and ideal for applications such as robotics, automation, and remote-controlled systems.
The primary objective of this repository is to develop and incorporate the hardware interface, enabling the utilization within the ROS2 (Robot Operating System) framework.


For a better understanding and simple control (outside ROS) of the micro servo, see my other github project [S90_servo_motor](https://github.com/mataruzz/raspberryPi_components_tests/tree/main/S90_servo_motor), or looks at other [examples](https://www.circuitbasics.com/how-to-use-servos-on-the-raspberry-pi/).
## Implementation
To control the servo position it has used the "ros2_control" framework, specifically implementing the ***forward position controller*** hardware interface.
In addition, it has been integrated the **WiringPi** library for communicate with the servo on the RaspberryPi.
## Configuration and Setup
To enable the utilization of this repository, the micro-servo S90's PWM wire must be connected to PIN 5 (GPIO's pin enumeration, corresponding to physical PIN 29).
### Used System
This repository has been designed for use with the following hardware and software:
- Raspberry Pi 3B+
- Ubuntu Server 22.04 LST
- ROS2 Humble
### Installation
Once the hardware connection is ensured, access to the Raspberry (e.g., SSH) and:
* Clone the wiringPi repository, since the installation from apt may not work, and build it:
```
cd ~/
git clone https://github.com/WiringPi/WiringPi.git
cd ~/WiringPi && ./build
```
* Clone the servo repository both on your PC (to visualize the simulation) and Raspberry (to send actual signals):
```
cd ~/
git clone https://github.com/mataruzz/ROS2_servo_motion
```
and install all the dependent libraries:
```
rosdep install --from-paths src --ignore-src -r -y
```
* Build the repository (limitating the number of threads) on the Raspberry:
```
cd ~/ROS2_servo_motion
colcon build --parallel-workers 2 --executor sequential
```
### Run the example
In the following example, 5 positions are defined and iteratively passed to the controller.
***Inside the RaspberryPi***:
* Source the ws:
```
cd ~/ROS2_servo_motion
source install/setup.bash
```
* Run the controllers:
```
ros2 launch ros2_servo_motion S90_servo.launch.py
```
* Run the example:
```
ros2 launch ros2_servo_motion test_fordware_position_controller.launch.py
```
Another way to send to the controller the target position is to write directly on the controller topic:
```
ros2 topic pub /forward_position_controller/commands std_msgs/msg/Float64MultiArray "data:
- 3.14"
```
The above example script nothing does more than sending to the controller the desired position every second.
***On your PC:***
* Open Rviz:
```
rviz2 -d ~/ROS2_servo_motion/src/description/config/config.rviz
```
You will see the following model:
## Expected result
If everything works as expected, you should be able to see the physical micro-servo S90 moving to 5 different positions ([0, 0.785, 1.57, 2.36, 3.14] rads), in loop.
In addition, the movement will be also simulated in the RViz environment, as shown below:
## **Pros** and **Cons**
To provide a clear and structured assessment, you can find pros and cons in the following table:
|
**Pros**
| **Cons**
|
|:-------------|---------------------------|
| **Hardware Integration:** The capacity to effectively communicate with physical devices is demonstrated through the construction of a hardware interface for the micro servo S90. | **Scalability Concerns:** You can run into scalability problems that need to be handled if you integrate more hardware or devices into your project.
|
| **Raspberry Pi Compatibility:** As a control platform, the Raspberry Pi 3B+ offers a variety of advantages, including as price, a strong community and ecosystem, and usability.
| **Limited Control Precision:** It is difficult to achieve high precision when feedback mechanisms is missing. Due to the lack of a closed loop control system, the current configuration of the project is susceptible to disturbances and inaccuracies in servo positioning, which can restrict precision and robustness. |
| **Open Source Framework (ROS2) compatibility:** Embracing ROS2 simplifies integration with hardware interfaces and opens a framework that is modular, reusable, and reliable. As part of the ROS2 community, you have access to a vast network of experts, collaborators, and enthusiasts. | **Lack of Trajectory Tracking:** The lack of trajectory control means that the servo cannot smoothly follow a predefined path or perform complex motions. This is often important in applications that require dynamic and precise behavior.
|
| **Position Control:** Achieving open-loop position control, even if simple and inaccurate, is an important part of advanced control technology and indicates progress toward project goals. | **Presence of Jitter:** A notable drawback is the presence of jitter caused by using an inaccurate square wave for control (generated by the RaspberryPi 3B+). This can lead to unwanted fluctuations and instability. |
## Future developement:
Looking to the future of this project, I would like to pursue several goals.
First, I want to enhance the functionality of the system by adding other servos and building a simple 2 degrees of freedom (2DOF) structure. This will provide me the ability to control a possible camera's movements in both the horizontal (right and left) and vertical (up and down) axes, which may be helpful for analyze the surrounding environment.
Additionally, I would like to explore other control methods, such as velocity control and, if practical, closed-loop control. Implementing these control approaches requires access to the necessary sensor data, such as potentiometer values, speed and time measurements.
Furthermore, I recognize the need to address system jitter, which can affect camera stability.