High performance Windows NT and DSP based system for the control of electrical servo-drives Objectives and concept The concept of the laboratory for servo-electrical drives has been developed in order to : ensure standard education of engineers in electrical servo drives, while using state of the art technology and user friendly tools offer high performance tools suited for engineers working on industrial projects related to electrical servo drives, allowing for instance rapid prototyping of new control strategies For the latter objective, engineers performing advanced studies in electrical servo drives, starting for instance at the torque set point level, need be in position to control the power stage downto the on/off command signals
students
Axis manager
developers, researchers
PC-NT4.0, application software
Position/speed/torque set point generator, position/speed/torque control, power stage logic signals calculation, measurements processing
DSP ("SHARC") board, PWM and A/D board on Easy (backplane) bus
Commercial or custom power stage
Power stage, sensors
Software oriented solution In order to satisfy both objectives, the solution has to offer a maximum of
flexibility for use and has to be easily configurable. Therefore, an almost 100% software realisation is clearly required, performing as many as possible tasks, including real time task management like position and torque control,
parametrisation, configuring, monitoring, visualisation and on line analysis by the means of modern and user friendly software tools.
Software updates allow therefore the use of state of the art technology for education at limited cost.
System structure overview The developed system rely on three digitally interconnected units : a high performance DSP board for real time tasks such as torque control a commercial power stage
a PC running under Windows NT4.0 for on line configuring, visualisation and analysis
G5(s)
U(s)
-
Σ
G1(s)
Σ
G2(s)
G3(s)
Y(s)
G4(s)
WINDOWS OLE
Measurements (currents, position, ...)
backplane bus "Easybus" e.g. MATLAB SIMULINK
Application RTPWatch
Algorithms, command strategy, signals & parameters NT driver
parallel port
...
PWM & A/D
6
Power stage
Controller
PC-PENTIUM-WINDOWS NT 4.0
3
Motor, load, sensor
DSP board "EasyDSP" "SHARC"
Hardware: DSP "SHARC" board and "Easybus" backplane bus DSP board "EasyDSP"
Backplane bus "Easybus"
It's quite difficult to customise commercial material down to the power stage
level. Therefore a high performance and easy to use DSP board (based on Analog Devices's "SHARC") has been developed. It can drive a commercial power stage (Atlas Copco Control's SAM).
The processor board can be plugged into an simple but fast backplane bus,
especially developed to make its interfacing as easy as possible. In this way, students or researchers are in a position to very simply realise and interface their own boards, for instance A/D converters, specials sensors, PWMs, aso.
A high performance processor is needed to allow students and researchers to rapidly implement their algorithms without spending time at code optimisation or translation tasks
Software : DSP SHARC and Windows NT
Real time software on the DSP "SHARC"
The DSP board is responsible for the execution of all real time tasks. For instance,
In this way, complete high performance position/torque control is easily
the current control is executed at sample frequencies of 10 [kHz] to 20 [kHz] or more, depending on application. The processing of torque set point, phases currents and position measurements produce the 3 switch on/off periods, which are digitally transmitted to power stage's PWM registers.
programmable through two well defined user routines. New control strategies are implemented in a very easy way without loosing performance.
The use of an high performance DSP allows to code the current control routine in
The user interface RTPWatch (Real Time Process Watch) for
high level language (C) although its execution time is limited to 20 [ms].
/*Scalar current controller for AC brushless synchronous machine*/ void regul_i(void) { …
MapMemPlus driver has been developed, data exchanges provide functionnalities such as : on line parameter variation; on line signal visualisation and analysis. "Standard" software components (scopes, buttons, a.s.o.) may be used to create dedicated control panels with popular tools such as Delphi or alike; direct link with other Windows NT applications such as MATLAB through OLE mechanism. This allows for on line use of sophisticated analysis tools.
/*Command law of PI controllers*/ us_1_c = Kp_i * (e_1 + Gi_i * int_e_1); us_2_c = Kp_i * (e_2 + Gi_i * int_e_2); … }
http://www.einev.ch/iai
program downloading, on line parameter setting signal monitoring, aso is based on a Windows NT4.0 application software.
Through an efficient link between DSP and the PC parallel port, for which the
/*Current errors and their integral*/ e_1 = is_1_c - is_1; e_2 = is_2_c - is_2; int_e_1 = int_e_1 + e_1; int_e_2 = int_e_2 + e_2;
References : M. Etique - prof. EIVD
Application software on Windows NT 4.0
in s t i t u t d ' Automatisation in d u s t r i e l l e
es s o
Haute Ecole Spécialisée de Suisse Occidentale
