usable simulink embedded coder target for linux -...

Usable Simulink Embedded Coder Target for Linux

Michal Sojka, Pavel Píša

Czech Technical University in PragueFaculty of Electrical Engineering

Department of Control Engineering

16th Real-Time Linux WorkshopOctober 12, 2014

Düsseldorf, Germany

M. Sojka, P. Píša Usable Simulink Embedded Coder Target for Linux RTLWS16 1 / 22

Motivation

I Not everybody is a programmerI Control engineers can design

control algorithms but cannotprogram them in C

I They use tools like Simulink to simulate their algorithmsI They still want to run their algorithms on real hardware, not

just simulationsI Solution: Matlab/Simulink + automatic code generationI Control applications = real-time applications

I while (1) { read input; calculate control; write output }

I The generated code needs to run on RTOS, e.g. GNU/Linux


Motivation




just simulations

I Solution: Matlab/Simulink + automatic code generationI Control applications = real-time applications




Motivation




just simulationsI Solution: Matlab/Simulink + automatic code generation

I Control applications = real-time applicationsI while (1) { read input; calculate control; write output }



Motivation




just simulationsI Solution: Matlab/Simulink + automatic code generationI Control applications = real-time applications




What is Simulink?

I Widely used tool for design and simulation of dynamic systemsI Commercial, non-free program – a part of MatlabI Developed by MathWorksI In its core is a solver of differential equationsI Algorithm is drawn as a data-flow graph (= Simulink model)I Simulink can simulate itI Simulink can generate C code of the model


Why people use it?


Code generation in Simulink

I Example:Sine Wave

Product

3

Constant

Pin 1

ErrFlag

Analog Input

Pin 1 ErrFlag

Analog Output

double in1, out1;in1 = adc_read(1);out1 = sin(t) + 3 * in1;dac_write(1, out1);

I Simulink Coder & Embedded CoderI Code generation target

I Template for “main.c”I Template for MakefileI I/O blocks


Can Simulink generate code that runs on Linux?

Yes, but. . .


Problems of Simulink code generation targets for Linux

I Very good support for popular embedded boards(Raspberry Pi, BeagleBone, . . . )

I Can only be installed on Windows hosts /I Other Linux targets are fortunately supported via “IDE Link”

I Uses Eclipse IDE to compile and run the code /I Slow! /

I Generated code uses POSIX timersI POSIX timers do not guarantee real-time properties (latencies)

even under preempt_rt /




I Can only be installed on Windows hosts /

I Other Linux targets are fortunately supported via “IDE Link”I Uses Eclipse IDE to compile and run the code /I Slow! /






I Can only be installed on Windows hosts /I Other Linux targets are fortunately supported via “IDE Link”

I Uses Eclipse IDE to compile and run the code /I Slow! /




POSIX timers under preempt_rt Linux

I POSIX timers use signals to notify user space about theirexpiration

I Signal delivery path uses sleeping locks under preempt_rtI Deferred to softirqI Softirqs are:

I executed in the context of arbitrary task or ksoftirqdI executed with random (e.g. non-real-time) priority


Is there better code generationtarget?

Yes

ERT_LINUX


ERT_LINUX code generation target

I Goal: Minimalist target which reuses as much Simulink codeas possible (not that easy)

I No Eclipse needed ,I Uses clock_nanosleep() for timing ,I External modeI Works both natively and with cross-compiling

http://lintarget.sf.net


http://lintarget.sf.net

ERT_LINUX I/O support

I MF624: PCI data acquisition cardI Digital IO, Analog IO, PWM outI Counters (can be used for PWM input!)I Incremental encoder inputI Based on UIO driver ⇒ no syscall overhead

I CAN bus transmit/receiveI Some support for Raspberry PiI No Comedi yet




I CAN bus transmit/receiveI Some support for Raspberry Pi

I No Comedi yet




I CAN bus transmit/receiveI Some support for Raspberry PiI No Comedi yet


Applications/demos


PMSM motor simulationHardware-in-the-loop (HIL) simulation

Infineon TriBoard running a motor control algorithmPC

Motor & fault simulation

MF

624

I/O

car

d

PCLinux, CANCAN attacks

Linux, preempt_rt

PCInfoneon DeviceAccess Server (DAS)

CAN bus

Inte

rfac

e bo

ard

USB(serial line,JTAG, ...)

I Analysis of how does security influences safetyI PMSM motor simulation @ 20 kHzI Hand-written motor control algorithm runs on real hardwareI Message authentication on CANbus + brute force attacks


Robot with parallel kinematic structure

I 4 DC motors, 4 incremental encoders, other I/OsI Presented at Embedded world 2014I Sampling period 1ms but complex computationsI More reliable that previously used Windows target


Motor control on Raspberry Pi

I Final task for students of our real-time course:I Create software motor controller on an embedded PowerPC

board with VxWorks

I Can the same be implemented on Raspberry Pi with Linux?


Hardware

PWM

GPIOsRasp

berr

y P

i –

P1

CHB

CHA

IRC

HI DRV

LO DRV

IN

HI DRV

LO DRV

IN

DCMOTOR

Motor Power Supply

DIR

I As simple as possibleI Four NOR gates (SN74HCT02)I H-bridge (L6203)


Incremental encoder (IRC) processing

I The most demanding partI IRC signal: 0 – 20 kHzI Every edge generates an interrupt (up to 80 k interrupts/sec)I Kernel driver to calculate the position

I Sustainable IRQ frequency up to ≈ 32 kHzI Further improvement: Use of ARM FIQ


Incremental encoder (IRC) processing

I The most demanding partI IRC signal: 0 – 20 kHzI Every edge generates an interrupt (up to 80 k interrupts/sec)I Kernel driver to calculate the positionI Sustainable IRQ frequency up to ≈ 32 kHzI Further improvement: Use of ARM FIQ


IRC processing details

GPIOs

Rasp

berr

y P

i

CHB

CHA

IRC

Hard IRQ

IRQ threadedhandler

I Position calculation works better if derived from the order ofIRQs than from the signal values read in the handler.

I FIFO run queue preserves order!


Demo: Raspberry Pi motor controller

sfIRCInput

IRC0

int32 0

IRC-display

Convert

IRC int32 to Real

double

IRC-scope

-0.01

ManualPWM

double

sfPWMwDirOutput

PWMwDirManualPWM

Control

double Opt. PSD Controller

w RSTsrred I

u

I P

Subsys PSD

double

0

PositionRequest

double

0

RESET

double

ActiveOutputRange

double-K-

AntiWindup

double

Position

double

Convert

To int

uint8

0.05976

PWM-display

Pos

Trajectory

double

PWM


Demo: Raspberry Pi & CAN


Conclusion

I ERT_LINUX target worksI Used in several applicationsI Does not suffer from serious problems as original MathWorks

code generation targets.I Limited support for I/Os – Blocks for Comedi are on our todo

listI It might be possible to use our target with other I/O blocks

(e.g. from MathWorks)

Thank you!


Conclusion

I ERT_LINUX target worksI Used in several applicationsI Does not suffer from serious problems as original MathWorks

code generation targets.I Limited support for I/Os – Blocks for Comedi are on our todo

listI It might be possible to use our target with other I/O blocks

(e.g. from MathWorks)

Thank you!M. Sojka, P. Píša Usable Simulink Embedded Coder Target for Linux RTLWS16 22 / 22

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