Haptics Paddle

This repo contains a K64F MCU program for Arvids's Haptics Paddle, a demonstration set-up for admittance control.

The set-up consists of a lever on top of a loadcell, attached by to a DC motor by string transmission. A microcontroller controls the motor with a desired haptic mode.

Usage

Interface

Connect the first micro-USB port (marked SDA USB) to your computer to power the board and do serial communication.

Also connect the second USB port (marked K64F USB) and use the uScope (HID version) to graph data.

Use the INT1 button to go to Idle mode. Use the RST button (next to the USB) to reset the board.
When in Idle mode, hold INT1 for about a second to go back to the regular run mode.

Parameters

You can use the serial terminal to change e.g. model parameters. Do this by typing entries like:

m=3.5

Read the serial start-up prompt for a list of parameters.

Hardware

• MBED K64F microcontroller
• Maxon DC Motor
• HX711 loadcell amplifier
• DFRobot 2x2A DC motor shield
• 9V or 12V DC adapter

On the HX711 development kit, the RATE pad on the bottom was broken, to increase the output rate from 10 Hz to 80 Hz.

The exact type of the Maxon motor is not known. It can be used with a 9V or 12V supply.

Calibration

The HX711 plus strain sensor were roughly calibrated by hanging a known weight from the end. The value found was 31 V/Nm. This won't be accurate, but should be the right order of magnitude.

Connections

The motor shield should be stacked on top of the K64F. The jumpers on the motor shield should be set to PWRIN, such that the external power supply is used.

The female 2.1 mm DC jack should be connect to the PWRIN +/- terminals on the motor shield.

The M1 +/- of the motor shield should be connected to the plus and minus of the motor. (The order of + and - for the motors will flip the direction but otherwise matters not.)

The Maxon motor encoder cable has 10 pins. The layout can be found in https://www.maxongroup.com/medias/sys_master/8815046230046.pdf, under 'Encoder Cable Connector J4'. Only +, -, A and B are needed.

On small HX711 breakout board, connect:

• GND to MCU ground
• VCC to MCU +5V
• DT to D2 on the MCU
• SCK to D3 on the MCU
• E+ to the sensor Vcc (red wire)
• E- to the sensor ground (black wire)
• A+ to the sensor output 1 (white wire)
• A- to the sensor output 2 (green wire)

On the K64F, connect:

• D2 and D3 to the amplifier (see above)
• D12 to encoder channel B
• D13 to encoder channel A
• GND and 5V to both the encoder and the HX711

Baked into the motor shield are the connections:

• D4 direction motor 2
• D5 PWM motor 2
• D6 PWM motor 1
• D7 direction motor 1

Compilation

The program can be compiled locally with MBED Studio, or using the online compiler at mbed.org.

MBED includes submodules through the .lib files. They are not literal Git submodules.