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FlexSEA-Execute 0.1: Advanced motion controller

A project log for FlexSEA: Wearable robotics toolkit

OSHW+OSS to enable the next generation of powered prosthetic limbs and exoskeletons. Let’s make humans faster/better/stronger!

Jean-François DuvalJean-François Duval 05/12/2015 at 17:430 Comments

At its core, the FlexSEA-Execute board is a BLDC motor driver. It is specialized for robotic and prosthetic applications. The high level design goals were to maximize the system integration (small physical dimensions, large number of integrated peripherals and interfaces, support for external input and output devices), allow fast communication and networkability via the use of a fast multi-drop communication interface, and have built-in safety features. The design went through three major revisions; this document focuses on the last generation (FlexSEA-Execute 0.1) (for more details (and pictures) about the previous designs, refer to The evolution of FlexSEA prototypes.)

The next figure presents the logical organization of the FlexSEA-Execute 0.1 board. In orange are the schematic sheets and in grey are the sub-circuits present on certain sheets.


The safety system is extremely important. The next diagram highlights the safety related features:

Electrical specifications

Supply voltage (V)

15-24V

Motor current (A)

20A Continuous

Intermediate supply

10V 500mA SMPS

Logic supply

5V 500mA SMPS

Motor

Type

3-phase brushless (BLDC)

Sensor(s)

Hall effect, optical encoder

Commutation

Block, Sinusoidal, FOC

PWM

12 bits 20kHz, 10 bits 78kHz or 9.65 bits 100kHz

Microcontroller

Reference

PSoC 5LP - CY8C5888AXI-LP096

Special features

Programmable analog and digital blocks

CPU/RAM/IOs/Package

80MHz ARM Cortex-M3, 256KB RAM, 62 IOs, TQFP

Software / IDE

PSoC Creator 3.1, mix of C (ARM GCC 4.7.3) and graphical programming.

Co-processor(s)

PSoC 4 - CY8C4245LQI-483

Serial interface

Type

3x Half-Duplex RS-485 (can be full-duplex synchronous)

Bandwidth

2-10Mbps

Onboard USB

Full-Speed (FS) 12 Mbps

Current sensing

Hardware

0.005Ω resistor

Software / control

20kHz Proportional-Integral controller

Safety features

Overvoltage

TVS will clamp at 36V

Overcurrent

Software protection

Locked rotor

Hardware - lead shorting circuit

Motor temperature

Hardware measurement

Board temperature

CPU + bridge temperature reading

Clutch

Variable voltage, 8-bits PWM, 400mA

Strain gauge amplifier

Dual stage, 500 < G < 10000, high CMRR

IO connector

Molex PicoClasp 40 positions, SMD 1mm pitch

External peripherals

IOs available

12

Digital IOs

Up to 12

Analog inputs

Up to 8 (12-bit SAR, 8-20-bits Sigma Delta)

Serial

I²C, SPI, UART

Other

1 optical encoder (A/B/I), 1 Hall effect encoder (3 pins)

Dimensions (mm)

X (mm)

49

Y (mm)

49

Z (mm)

From 12 to 15mm depending on capacitors

PCB technology

Layers

6

Copper

1 Oz

Trace/space/via

5/5 mils trace/space, 8/20 mils blind vias

Assembly

Double-sided

Other

6-axis IMU, RGB LED

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