Servo and Motor Controller Date: August 10, 2004 Description: The servo motor controller drives three R/C servomotors and one brushless DC motor. All four motors are controlled by PWM signals sent from a PIC 18F252 micro-controller. The PWM signal to the brushless motor is used to toggle on/off an Allegro A3936 three-phase PWM motor driver. The servo controller regulates the shaft velocity of the brushless motor with encoder feedback, which is decoded by an HCTL2000 quadrature decoder. An in-circuit serial programming connector is provided on the PCB to allow for in board reprogramming of the PIC micro-controller. PCB Block Diagram: Power Consumption: Logic Supply: 5V (max current: 1.75 A) Motor Supply: 24V (operates between 15V – 50V, max current: 3A) Data Interface: TTL-level 3-wire serial

Microcontroller (PIC18F252)

R/C Servo

R/C Servo

R/C Servo

PWM motor Driver (A3936)

3-Phase Brushless

Motor

Quadrature Decoder (HCTL2000)

Serial Comms

5V Logic Supply

24V Motor Supply

Hall Sensors

Encoder Feedback

Control System: The DC motor sends out encoded position signals to the quadrature decoder chip. The microcontroller reads the position feedback information from the decoder and converts it into a velocity reading. This velocity data is then compared to the desired speed and an error signal is generated, which is used to calculate the PD compensation. Circuit Schematics:

C120

22pF

C121

22pFVCC

VCC

J6

RS232(TTL)

123

RX

TX

GND

DIR

C22

0.22mF

C3

C1

C2

U23

HCTL2000

D0 1

CLK2

SEL3OE4

RST5

CHB6 CHA7

GN

D8

D7 9D6 10D5 11D4 12D3 13D2 14D1 15

VCC

16

C400.1uF

J14

Serv oMotor1

123

J15

Serv oMotor2

123

J16

Serv oMotor3

123

C500

.1uF

VCC

J4

Motor Signals

12345678

5v

GND

A

B

Z

C1

C2

C3

ENABLE

VCC

J1

HEADER 5x2/M

246810

13579

VCC

C300

.1uFU35

PIC18F252

Vpp1

RA0/AN02

RA1/AN13

RA2/AN2/VREF-4

RA3/AN3/VREF+5

RA4/T0CK16

RA5/AN4/SS/LVDIN7

VSS18

OSC1/CLK19

OSC2/CLO0/RA610

RC0/T1OSO/T1CLKL11

RC1/T1OSI/CCP212

RC2/CCP113

RC3/SCK/SCL14

RB1/INT1 22

RB0/INT021

VDD 20

VSS219

RC7/RX/DT 18

RC6/TX/CK17

RC5/SDO 16

RC4/SDI/SDA15

RB7 28

RB627

RB5 26

RB425

RB3 24

RB223

signal_groud

C301

.1uF

U26

MX045 Oscillator

Output enable1

GND2Vcc 4

Output 3

Y1CRYSTAL/SM

Schematic 1: Logic Section

Controller (PIC18F252)

Plant (Motor)

Desired Speed

Shaft Velocity

Encoder

-

R1351K

VDD

R710K

VDD

VDD

VBB

R810K

VDD

R910K

C110.22mF

VDD

VDD

+ C61 mF

J5

Motor Power

12

J7

Logic Power

12

VBB

C3

C2

C1

Hall Sensors

signal_groud

R120.25OhmC7

0.22mF/100V

D9

GND11

GND22

HA+3

HA-4

HB+5

HB-6

HC+7

HC-8

VDD9

REF10

GND311

GND412

GND513

BRAKE14

SENSE15

SR16

OUTA17

HBIAS18

VBB119

LSS120

OUTB21

GND5a22

GND1144

PFD143

PFD242

BLANK41

EXTMODE40

ENABLE39

DIR38

Vreg37

OSC36

GND1035

GND934

GND833

SLEEP32

CP231

CP130

Vcp29

OUTC28

TACH27

VBB226

LSS225

GND724

GND623

D8D7DIODE SCHOTTKY

J2

MOTOR

123

VBB

ENABLE

+ C833 mF

D10

DIODE SCHOTTKY

DIR

D11 D12

C200.22mF

R52K

R62K

VDD

C90.22mF/100V

Schematic 2: Power Section

PCB Drawings

Figure 1: PCB Layout – Top

Figure 2: PCB Layout – Bottom

Bill of Materials:

Name Value Footprint Notes Vendor Part # # per Board

C6 1uF, 100V Cylinder Electrolytic Digi-Key P5589-ND 1C7, C9, C11, C20, C22 0.22uF, 50V SM/C_1206 Ceramic X7R Digi-Key 399-1251-1-ND 5C8 33uF, 100V Cylinder Electrolytic Digi-Key P5595-ND 1C120, C121 22pF, 50V SM/C_402 Ceramic Digi-Key PCC220CQCT-ND 2C300, C301, C400, C500 0.1uF, 50V SM/C_805 Ceramic X7R Digi-Key 399-1170-1-ND 4D7, D8, D9, D10, D11, D12 Diode, 100V, 1A SM/D Fast Recovery Digi-Key FR1BDICT-ND 6J1 Connector 5x2 2mm ICSP connector Digi-Key 1J2, J6, J14, J15, J16 Connector 3x1 2mm

Brushless motor 3-phase power Digi-Key

H2084-ND (Recepticle)H2106-ND (Header) 5

J4 Connector 8x1 2mm

Brushless motor logic and encoder feedback Digi-Key H2133-ND (Header) 1

J5, J7 Connector 2x1 2mm 24V motor power Digi-Key H2083-ND (Recepticle)H2105-ND (Header) 2

IC socket 8 pin Holds half HCTL200 Digi-Key AE8908-ND 2

R5, R6 2K SM/R 402 1% 1/16W Digi-Key P2.00KLCT-ND 2

R7, R8, R9 10K SM/R 402 1% 1/16W Digi-Key 311-10.0KLCT-ND 3

R12 0.25Ohm Radial Current-Sense Res Digi-Key 15FR250-ND 1R13 51K SM/R 402 1% 1/16W Digi-Key 311-51.0KLCT-ND 1U23 HCTL2000 Through hole Quadrature Decoder 1U26 10MHz OSC SMD HSM938H Digi-Key CW303-ND 1U35 PIC 18F252 SOIC 28 pin Microcontroller Digi-Key PIC18F252-I/SO-ND 1Y1 10MHz Crystal SMT Can ATS100SM Digi-Key CTX508-ND 1

Brushless Motor 24V, 40W, Encoder

Shinano Kenshi LA052-040E-3NL1 1

Resettable fuse 1.25A 15V SMD MF-SM123CT-ND 1

Overview of Code: The program for the PIC is broken up into the three sections: Main program, Low Priority Interrupt Service Routine, High Priority Interrupt Service Routine INITIALIZATION Configuration Bits: Oscillator set to HS (10MHz) Disable all other bit word settings Configuration Variables: Motor speed Max = -3200rpm to 3200rpm Motor PWM period = FF (255 clock cycles) Max motor duty cycle = 1000 Fin position = 3000 to 5000 (4000 is initialized position) Baud Rate = 57.6k Internal clock = 10MHz MAIN PROGRAM While loop overview: Wait for new command to be sent Poll motor speed and correct if necessary Send out PWM signals to three fins Returns motor speed and PWM signals Processing Command: Once command is received from DimmPC it is searched for each element Format of command: aXXXXbXXXXcXXXXmXXXX (All or portions of the command may be sent) Each element is saved into a variable to be implemented in the ISR’s If “x” is sent new speeds are not returned If “e” is sent speeds are returned No Command is sent: Until a new command is received the speed is continuously polled and updated After each speed check, the speed and PWM signal is returned to the user. HIGH PRIORITY INTERRUPT Triggered by Fins Flag: 6 step cycle: Set fin a high, Set fin a low Set fin b high, Set fin b low Set fin c high, Set fin c low One step is implement each ISR is called due to Triggered by command: When a command is received, the receive buffer triggers this ISR

The ISR then saves and receives the data into a command buffer The received command flag is set so the main while loop will process the command when ISR exits

LOW PRIORITY INTERRUPT Triggered by Motor Flag: Reads the decoder chip and exits ISR (repeats 10 times) Read decoder 10 times (multiple reads decreases error) Convert data to rpm (freq of 10th read = 10.1Hz) Compare with goal speed to get speed error Calculate speed comp based on error Update duty cycle and direction Triggered by Communication Error: If no command has been received in the past two seconds, the motor speed is set to zero and the fins are set to 4000 (center). This is a fail safe to stop the AUV in the event that there is a communication problem between the DimmPC and the motor control card.

PCB Pictures