Verdant Robotics, 2023
A new generation of up-sized robotic crop sprayers necessitated a multi-channel hydraulic actuation solution to maintain its wings at a consistent height above ground. Building on an interim passive system, a fully-automated design with closed-loop sensor feedback was developed.
This was a very interesting and challenging project that allowed me to greatly develop my skills in hydraulic system design and control.
Actions:
In consultation with all stakeholders, I generated a detailed requirements document with specific emphasis on safety. I then took a system-level design approach to define the necessary functions and subsystems. I took this design and worked with outside vendors to down-select components on the bases of function, supply chain availability, development speed, and value.
The essential components of the design are:
- Bosch-Rexroth BODAS off-highway controller/PLC (CODESYS version)
- Bosch-Rexroth BODAS ultrasonic sensors and controller
- Bosch-Rexroth 4-channel proportional valve stack
- SICK CANopen rotary encoders
A project plan was created with several milestones based on realization of key functionalities:
- Open-loop control
- Closed-loop control utilizing rotary encoders
- Multi-actuator coordinated motion for stowing and deploying operations
- Closed-loop control utilizing ultrasonic sensor height measurements
- Field readiness, emphasizing integrated and validated safety checks
I dove into the controller’s documentation to familiarize myself with its operation and limitations, and designed a wiring schematic to meet the requirements. I taught myself the CODESYS programming environment and CANopen protocol. I then coded and debugged an open-loop control program, and built a prototype.
Results:
This project is ongoing. As of this writing, open-loop control has been successfully demonstrated and validated. Sensors for closed-loop control have been integrated into the system, and closed-loop control is ready for testing.
Matt Mundell 