NicaDrone is announcing the 3rd generation of electro permanent magnet developed with Zubax Robotics with a bunch of new features.
First a crappy video:
The OpenGrab EPM v3 is an electropermanent magnet, combining the advantages of electro and permanent magnets. The device creates a very strong magnetic contact with a ferrous target. It supports UAVCAN, RC PWM and push button operation. OpenGrab EPM v3 has been developed by NicaDrone in cooperation with Zubax Robotics.
Theory of operation
The NXP LPC11C24 MCU drives a mosfet connected to a transformer in a flyback configuration to charge the main PET capacitors up to 475 V.
A thyristor bridge is used to discharge the capacitor in either direction through the winding inside the AlNiCo material. This results in a short, 20 us 300 A pulse creating a 100 kAm field in the AlNiCo material. This causes the magnetic domains in the AlNiCo magnets to align in a particular orientation to form a magnetic circuit with a ferrous target.
An ON command results in the charging and discharging the capacitors 3 times to achieve full magnetization.
An OFF command results in charging and discharging the capacitors several times with changing direction and decreasing amplitude, effectively degaussing the AlNiCo material.
- Cargo lifting in UAV and robotic applications.
- Robot workholding.
- Education, demonstration of magnetic properties.
- Steady state power under 50 mW
- Short cycle time
- Variety of interfaces:
- RC PWM
- Push button
- Open source firmware and hardware
- 5 V supply voltage, can be powered via RC PWM connector or via UAVCAN port
The diagrams below document the mechanical arrangement and dimensions (click to enlarge):
|Tcycle(ON)||Time to complete one cycle||0.75||s|
|Tcycle(OFF)||Time to complete one cycle||1.2||s|
|Fmax||Max holding force||200||N|
|Isteady||Steady state current draw||10||mA|
|Ipeak||Peak current draw during cycle execution||1000||mA|
|m||Mass of the device||65||g|
|RHoperating||Operating humidity (non-condensing)||0||75||%|
For debugging we recommend the Zubax DroneCode Probe, a multi-purpose debugger for STM32 and other Cortex-M based microcontrollers. It allows one to test and debug firmware on the microcontroller and is compatible with majority of IDEs (Eclipse and derivatives, CodeBlocks, etc.). Zubax DroneCode Probe is equipped with DroneCode-approved connectors which enables seamless compatibility with DroneCode projects such as Pixhawk and NicaDrones EPM V3.