RPi 4 based mobile bot features optional 6-DOF arm

RPi 4 based mobile bot features optional 6-DOF arm

Jul 28, 2021 — by Eric Brown

— 368 views

Elephant Robotics’ $700 to $1,200 “MyAGV” mobile robot runs on a Raspberry Pi 4B with a 360° lidar, 5MP cam, a 220 rpm/min motor, 4x omnidirectional wheels, and an optional 6-axis MyCobot arm.

In May, Elephant Robotics launched a $699, six-axis manipulation bot called the MyCobot Pi, which is built around a Raspberry Pi 4 Model B. Now the company has given its robot arm some wheels in the form of a MyAGV autonomous ground vehicle (AGV), which houses its own RPi 4B. When the $699 mobile bot is equipped with an MyCobot arm, the system is billed as the world’s smallest, 6-DOF compound robot.

MyAGV (left) and with optional MyCobot M5 arm
(click images to enlarge)

The MyAGV provides a 360° for autonomous SLAM navigation. A 5-megapixel camera can help guide the optional MyCobot arm for precise gripping. As with the MyCobot Pi, the MyAGV is controlled by a robotics stack that combines Debian Linux with Robot Operating System (ROS). You can use the software to enable multiple MyAGV bots with multiple arms all working in unison with real-time controls.

Two optional 6-DOF (degrees of freedom) robot arms are available: the original, ESP32-driven MyCobot M5, which sells on its own for $599, and the Pi-powered MyCobot Pi, which offers identical mechanical components and sell sfor $699. Each is discounted by $100 from the standalone price, so the M5 combo costs $1,198 and the Pi combo $1,298.

MyAGV rear views – numbers at right refer to 1) Lidar, 2) power button, 3)charging port, 4) micro-HDMI
(click images to enlarge)

The computerized base units of the optional arms are mounted on the top of the MyAGV via one of two LEGO connectors, enabling you to load two MyCobot arms at once along with “peripheral actuators.” A response to our queries from Elephant Robotics suggests that the arms’ ESP32 and RPi 4B computers, respectively, are typically subservient to the Pi inside the MyAGV, but can also be active and can collaborate with the main computer:

“The Raspberry Pi on the AGV will be doing the calculation from both cameras on car and robot arm,” replied the Elephant Robotics brand manager Henry Lin. However, “SLAM Lidar and the movement algorithm [running] at the same time could sometimes freeze the chips,” continues Lin. “So we recommend that users who are trying the to apply the camera on robot arm with a complex vision algorithm choose myCobot Pi so part of the calculation can be done separately and have better performance.”

Connecting MyAGV to MyCobot M5 (left) and connecting a top-mounted touchscreen
(click images to enlarge)

The diagram above shows how to connect to the base-level MyCobot M5 arm via USB Type-C and a separate power connection. It is still unclear if the MyCobot arms’ capabilities are fully available when used with the MyAGV. For example, there is no mention of the MyCobot M5’s 2-inch screen. The documentation does, however, show how to attach a small, apparently off-the-shelf, touchscreen to the top of the device, driven by an exposed micro-HDMI port. Other instructions show how to link the robot to a PS4 gaming controller.

The 3Kg, 300 x 205 x 145mm MyAGV is equipped with a Hall encoder motor that operates at 220 rpm/min. The motor drives 4x omnidirectional “Mcnamu” wheels at 0.9 meters per second. The independently controllable wheels enable the mobile bot to move forward, transverse (sideways), oblique, in rotation, or in a combination of multiple movements.

The Mcnamu rollers are arranged at a 45-degree angle with the axis and are installed in the outer ring of the wheel to contact the ground. When rotating, the friction produces a 45-degree reverse thrust with the axle. This oblique thrust can be divided into longitudinal and transverse vectors.

The omnidirectional, 360° Lidar — the blue hockey puck under the roof — enables SLAM navigation. Together with the front-mounted 5MP camera, the imaging system offers an 8-meter identification range. The supplied software uses ArUco binary square markers to enable precise calibration and positioning. Once you have set up a marker in the software, you can print it out and attach it to an item to be manipulated.

MyAGV GPIO pinout (left) and SLAM software
(click images to enlarge)

On the rear of the unit is the micro-HDMI port, power button, and charging jack to the 24V/1A supply. Directly above, a customized set of GPIO pins are exposed. A USB Type-C port on the side can connect peripherals such as a keyboard and mouse. It can also power peripherals such as a mounted touchscreen.

The MyAGV is said to be a collaboration with Hua Wei, which the Tom’s Hardware post that alerted us to the launch spells out as the Chinese tech giant Huawei.

Further information

The MyAGV is available starting at $699 at the Elephant Robotics’ shopping page. More information may be found in the wiki.