WinchBot 1.5

The video about WinchBot 1.5

Figure 1:
RS-components was looking for an interesting project to display on the SPS IPC Drives in Nürnberg, Germany. So the idea was born to create an improved version of this special robot with it's gripper is moving along the coordinates by three winches. Core element of the new model are bipolar stepper motors, replacing the geared DC motors with encoder feedback of the previous WinchBot. The advantage is a clearly lower step width of those motors.

Parts list

My WinchBot originates from a cooperation with RS-Components which is why links in the table point to their online shop.

Part	Pieces	RS Components	Remark
Raspberry Pi Model 3	1	896-8660
Stepper motor 1.68A at 2.8V	3	892-8732	Stepper motor winches
Geckodrive G250X	3	896-8553
Mount plate and heat sink for G250X	3	896-8557
Stepper motor 400mA at 12V	2	191-8299	Stepper motors gripper plattform
L293D	2	714-0622	Driver ICs Stepper motors gripper plattform
Standard Servos	3	781-3058	Servos gripper
5V power supply	1	124-2200	5V for Servos and Raspberry Pi
12V power supply	1	776-7738	12V for stepper motors
Gearwheel 80 teeth	3	521-7691	Gearwheel cable winches
Gearwheel 12 teeth	3	521-6193	Gearwheel stepper motors. Note: this gearwheel has an inner diameter of 6mm while the motor shaft of the steppers have a diameter of 5mm. Use either a piece of a tube to enlarge the shaft diameter or a gearwheel with a 5mm drill hole!
Ball bearings 6mm inner diameter	12	618-9913	Linear bearing of center square tube and bearings of cable drums.
Ball bearings 3mm inner diameter	3	492-1939	Strain relif cables
Schielded cables	1	529-582	Cablings
Hexagon nuts M6	1	525-919
Threaded rod M6	1	530-321
Plastics sheets 5mm	3	769-8749
Aluminum square tubes 20x20x100mm	5		Frame
Aluminum square tube 25x25x100mm	1		Center tube of WinchBot

Mechanics

Figure 2:
I have cut the 5mm plastic sheets with my CNC v3.2.

Figure 3:
The central linear guide is smaller that that of my first WinchBot.

Figure 4:
The parts for the cable winches have been modified for the bipolar stepper motors.

Figure 5:
I am using gearwheels from RS-components for the transmission at the winches.

Figure 6:
Same as before, I had built the lower part with the gripper using 5 servos, however after a first test run I replaced two of them with...

Figure 7:
...smaller bipolar stepper motors to reduce oscillations caused by the servos.

Figure 8:
I had to redesign the frame of the gripper part after another test to make the construction more sturdy.

Figure 9:
Caused by the higher weight of the gripper part, the steel cables running through tiny wire loops were fraying. To reduce strain on the cables I have added tiny ball bearings.

Figure 10:
The triangular frame hanging on the ceiling is stabilized by cords running crosswise. That reduces oscillations of the frame - without the cords, the WinchBot would become a large pendulum because of the high mass of the gripper part with the stepper motors.

Electronics

Figure 11:
5 stepper motors with driver chips, 3 servos and a Raspberry Pi model 3 are needed to drive WinchBot 1.5.
The stepper motors at the winches draw a current of 1.68A at 2.8V and they are driven by Geckodrive G250X in 10 microsteps per full step.
The stepper motors at the gripper platform draw a current of 400mA at 12V, so they are weaker but not as heavy as the winch motors. They are drivem through L293D chips in full steps.
The servos are used to rotate and open or close the gripper.

Figure 12:

Software

Figure 13:
Same as before I am using a browser interface to control WinchBot 1.5, however there are many improvements. With that interface, you can program sequences from all operating systems on many devices. Here I am using a Nokia 3 and even with this entry level smartphone you can control the Winchbot easily. The web server "Apache" with Perl support is running on the Raspberry Pi. By connecting a bluetooth keyboard and installing a simple text editor as well as an secure shell client on the smartphone, you can edit and compile all source codes used for my WinchBot. You don't need gigabytes of software or expensive hardware to do robotics - as you can see it all works even with this tiny pocket computer - as long as you are smarter than your phone...
You can get the software including scematics at the column download.

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