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Knuckle Arm Truck (2014)

Knuckle Arm Truck (2014)

Since the Merkur is quite heavy building kit thanks to the metal pars, it is often quite difficult to move the parts using week motors and transmissions. Finally, I chose to buy two sets of Lego Technic in order to have a small base for building my creations.

The first creation I chose to build was the knuckle arm truck. I must say that I am very satisfied with this truck in the retrospective. The truck is controlled by ARM Cortex M4 manufactured by STM. The instructions are sent from my own remote controller. All used peripherals (but to XBee) are built by myself.

I started the construction by building the moving arm which is the most important for the truck and is also the most difficult to build. The arm consists of two pistons used to move the arm and a grabber on its end to pick up a cargo. The grabber is moved using servo motor. The pistons are driven using two motors which need to be connected to them. Drive functions are thus routed through the arm rotation mechanism where one axle is routed in the cavity of the second one.

The next challenge was to mount the motors into the construction. Since the motors vibrate a bit thanks to my own Merkur -> Lego converter, I attached them to the construction using rubbers. The construction consists totally out of four motors (pistons, drive and arm rotation) and two servos (grabber and steering the wheels).

The last step was to add LED diodes as lights. Diodes are inserted directly into holes in the Lego parts after a small modification using a drill. Then, I could start to add the peripherals and to connect them to the motors, diodes and the processor. This process took me probably the most time because I had to produce a large amount of connecting wires.

And what does it do?

The bright reader already knows the entire functionality of the described truck, but I will summarize it anyway. The truck can drive both forwards and backwards with custom speed control. The truck can surely steer the front wheels. Parts of this vehicle are also front, rear, brake lights and two winkers.

The main functionality lies in the arm manipulation. This arm has 4 degrees of freedom: it can be rotated by 360 degrees, the large piston lifts the grabber and the small piston moves it away from the truck. The last degree represents opening the grabber. (The arm has 5 degrees of freedom physically, because the grabber is directed to the ground by the gravity.)

Pictures, schemes, videos

Click the image to show it in higher resolution
Arm with pistons
Axles for piston control
Wheel drive differential
Rear lights
Mounting of arm and motor used for rotation
Steering using servo motor
Rough construction of the truck
Front lights
Finished cabin
Wiring of peripherals to the processor
Final assembly of peripherals and processor
Completed truck
Wires used during construction
Tamyia transmission used for pistons control
Design of drive functions trough arm mounting

Source codes

Click the label to show the source code
KnuckleArmTruck.c: main file

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