Internationalof Computational
Intelligence
Systems
Journal ofJournal
Robotics,Networking andArtificial Life
Vol. XX(Z);Month(Year),xx–yy6(4); March(2020),
pp.pp.
254–257
DOI: 10.1080/XXXXXXXXXXXXXX; ISSN
online
DOI: https://doi.org/10.2991/jrnal.k.200221.005;
ISSNXXXX–XXXX
2405-9021; eISSN
2352-6386
https://www.atlantis-press.com/journals/ijndc
https://www.atlantis-press.com/journals/jrnal

Research Article

X–Y Platform Synchronous Control with CANopen
Chung-Wen Hung1,*, Yu-Ming Guan1, Shih-Ting Yu1, Wen-Hua Hu2
Department of Electrical Engineering, National Yunlin University of Science and Technology, No. 123 University Rd. Section 3,Douliu, Yunlin 640, Taiwan (R.O.C.)
2
College of Future Bachelor Program in Interdisciplinary Studies, National Yunlin University of Science and Technology,
No. 123 University Rd. Section 3, Douliu, Yunlin 640, Taiwan (R.O.C.)
1

ARTICLE INFOABSTRACT

Article History

An X–Y platform synchronous control with CANopen is proposed in this paper, and the platform includes a three-phase
stepping motor, motor controller and driver. The Controller Area Network (CAN) Bus is adopted for communication, and theCANopen protocol is also implemented for control. Moreover, both CiA301 standard for communication and CiA402 standard
for motor control are support. The interpolation mode in CiA402 is used for synchronized control of the X–Y platform, however,
Cross-Coupling Control (CCC) is proposed to improve the precision of synchronized control. The experimental results show
the proposed CCC perform higher accuracy than interpolation control. The phenomenon of more position error when higher
speed is also discussed.

Received 24 October 2019
Accepted 06 December 2019
Keywords
Controller area network
CANopenX–Y platformsynchronous control
cross-coupling control© 2020 The Authors. Published by Atlantis Press SARL.
This is an open access article distributed under the CC BY-NC 4.0 license (http://creativecommons.org/licenses/by-nc/4.0/).

1. INTRODUCTION
With the vigorous development of industry, production efficiency
and precision machining are more and more important. And, thehigh precision position control has become the main development
trend of motion control. The key point of the previous discussion
is detailed in this paper, such as three-phase hybrid stepping motor,Controller Area Network (CAN), X–Y platform.
Due to permanent magnet and toothed magnetic structure, the drivers of stepping motors could be triggered by pulses only. The open
loop system could be performed easily for lower-accurate position
control but keep constant torque [1]. However, to increase theaccuracy, an encoder is installed and close-loop control is considered for higher precision [2,3] measurement the peak of drivercurrent and control the driver current to keep the stable torqueand avoid out of step. And Space Vector Pulse Width Modulation,
SVPWM, is developed for higher accuracy with the high resolutionstep angle. The algorithm could perform an approximate sine-wave
current, and the motor will be driven more smoothly. The SVPWM
is implemented in this paper to perform motor driver voltage.
CAN Bus is popular for robotic control communication, because
it is a real-time, fast response and low-cost distributed communication [4]. CANopen is a communication protocol based on CAN
Bus, and also is device profile specification for automation, suchas CiA301 standard for communication and CiA402 standard for
motor control [5]. For compatibility and control performance,
CANopen is adopted for synchronized control of the X–Y platformin this paper.
Corresponding author. Email: wenhung@yuntech.edu.tw*

About multi-motor synchronized control, most literatures proposed parallel or series control [6] indicated the position error
or contour error are caused by the response and load difference
between motors, if the multi-motors are controlled independently.
For this issue, a parallel control with a compensator as Figure 1
was proposed in Koren [7]. The compensator would provide a
synchronized adjusted error, then control accuracy would beincreased obviously.
Parallel control and CCC will be compared in this paper. The interpolation mode defined in CiA402 will be adopted in this parallel
control to reduce the synchronized error between the two independent motors. Two control methods will be detailed.

2. SYSTEM ARCHITECTURE
The hardware of the system is shown as Figure 2, the proposedsystem includes two three-phase hybrid stepping motor anddriving blocks and three controllers. The slave controller isimplemented with an Renesas Rx62T microcontroller, and themaster could be a microcontroller or PC. In CCC mode, theerror of the other axis motor is necessary. In this paper, a user
defined object in CANopen is adopted to exchange the information between the two motors.
A microcontroller, Renesas RX62T, is used to control and driver
motor in this paper, and the used pins and peripherals of RX62T
are shown in Figure 3. The three sets of PWM signals are used tocontrol gate drive circuits, the required signals for three-phases six
switches is generated. And, the build-in CAN peripheral is used torealize CAN communication and CANopen protocol.

C.-W. Hung et al. / Journal of Robotics, Networking and Artificial Life 6(4) 254–257

255

Figure 1 | Cross-coupling architecture [7].

Figure 4 | Interpolation mode.

Figure 2 | System architecture diagram.

Figure 5 | The simplified arc cross-coupling control scheme.
Figure 3 | Pins and peripherals of RX62T.

3. SOFTWARE DESIGN
The proposed system adopts the CANopen as the system communication. CANopen is an application layer protocol built on theCAN’s physical layer and data link layer. The basic CANopen device
status and communication protocol are defined in CiA301 [4],and specification of motion control is defined in CiA402 [5]. Thecontrol methods proposed in this paper is CCC, and Interpolated
Position (IP) mode defined in CiA402 is also implemented in thispaper for performance analysis. Moreover, CANopen devices could
communicate through process data object, which provide a fastparameters delivery between the mater and slave, or between any
two slave devices.

3.1. Interpolated Position Mode
Interpolated position mode is a location control method, which
is a kind of linear interpolation, as shown in Figure 4. The Xn iscurrent position, Xn + 1 is the target, and the synchronized intervaltime, TSI, indicates the time difference between this two points.
The interpolation time period can be set by interpolation objectof CANopen, it is the time interval for next interpolated point,Xinterpolation, which is calculated from Equation (1), A first in,first out structure is implemented as the IP buffer in this paper,and is realized in the circular structure. The IP mode implemented in this paper could improve the position synchronizationand increase the position accuracy for two-axis motors.	    Xinterpolation =T( X n +1 − X n ) + X n TSI(1)3.2. CCC ModeIn this mode, two slave devices will exchange their position andspeed information by the user defined object, then CCC will compensate the error based on two-axis errors. The tweening method is
simplified to Figure 5 scheme, and the new speed and position will
be calculated by cross-coupling Equations (2) and (3) [8].
1	   X N +1 = E X - Dq (EY ) - (E X )(Dq )2 NNN212		   YN +1 = EYN + Dq ( E XN ) - ( EYN )( Dq ) 2(2)(3)

Here, XN + 1 and YN + 1 the two-axis target positions respectively;
EX and EY are the X-/Y-axis error between current and target posiN
Ntion respectively; and Δq is an angular displacement.

256

C.-W. Hung et al. / Journal of Robotics, Networking and Artificial Life 6(4) 254–257

4. EXPERIMENTAL RESULT

Table 1 | RMS (mm) of IP and CCC mode

The CANopen master, the RX62T board is shown in Figure 6, andthe three-phase hybrid stepper motor and driver circuit board areshown in Figure 7.

Time mode (s)IP mode (mm)
CCC mode (mm)The experiments are set for a circular motion control with a 50-mm
radius, three consecutive cycles in five different rotational speeds andtwo different control ways. The average Root Mean Square (RMS)of error between command and actual position is shown in Figure 8and Table 1. The lower rotational speed, the smaller RMS error in theInterpolated Position mode and the CCC mode. The RMS errors are
the almost same for all speeds under the Interpolated Position mode,
however, the CCCs’ are obviously reduced when the speeds slow down.

940.0569
0.05011250.0528
0.0424188
0.04750.0356376
0.04620.0237

Table 2 | The counts of reached target at different synchronized (Sync.) time
IP Sync. time
ReachedUnreached

210 ms

260 ms

350 ms

500 ms1000 ms

265
95355
5360
0360
0360
0360
0360
0

CCC Sync. time
ReachedUnreached

Figure 6 | CANopen master.

790.0585
0.0526106254

26298334
26

To investigate the reason why RMS error increase when speed up in
the proposed CCC mode, a target reached object which is defined in
CiA402 to indicate the motor driver reaches the new position command or not. Because the time duration is shorted when the synchronized period is reduced, the position target may not be finished.
The unreached command counts under two different control areaccumulated and shown in Table 2. Note, when synchronized time<350 ms, the unreached points will increase dramatically, it means theRMS error will increase under high speed. However, if the motor runs
under the system speed capability, CCC will be better than IP control.

5. CONCLUSION

Figure 7 | Motor and driver circuit.

A multi-axis synchronous control system based on CANopen isproposed in this paper. The standard CiA 301 and CiA 402 arealso supported by the proposed system. The experimental resultsof circular motion show both the Interpolated Position control
and CCC perform high accurate control, and the CCC mode has
smaller error than Interpolated Position mode when lower rotational speed. However, the CCC provide better synchronous control accuracy under the system support speed.

CONFLICTS OF INTEREST
The authors declare they have no conflicts interest.

ACKNOWLEDGMENTS
This work is partially supported by the Ministry of Science andTechnology, ROC, under contract No. MOST 107-2218-E-150-007,
107-2622-E-224-018-CC3 and 108-2218-E-150-004.

REFERENCES[1]

Figure 8 | Time for executing a circular motion in two different modes.

J. Zhu, G. Liao, Design of multi-axis motion control system
for stepping motor, 2010 WASE International Conference onInformation Engineering, IEEE, Beidaihe, Hebei, China, 2010,
pp. 23–26.

C.-W. Hung et al. / Journal of Robotics, Networking and Artificial Life 6(4) 254–257

[2]

[3]

[4]
[5]

B. Liu, P. Fransson, A. Ronquist, B. Winroth, Compensation ofload-dependent position error for a hybrid stepper motor, 2017
IEEE International Conference on Mechatronics and Automation(ICMA), IEEE, Takamatsu, Japan, 2017, pp. 846–851.
W. Xu, H. Kaizheng, X. Bin, Design for step motor control system
of automatic biochemistry analyzer, 2007 8th International
Conference on Electronic Measurement and Instruments, IEEE,
Xi’an, China, 2007, pp. 1-607–1-612.
CANopen application layer and communication profile, CiA 301,
Version: 4.0.2, 2002, pp. 15–87.
CANopen device profile for drives and motion control, CiA 402,
Version: 3.0, 2007, pp. 49–118.

[6]

[7]
[8]

257

S. Jee, H. Lee, J. Byun, D. Sung, T. Jang, Modular cross-coupling
controller for 5-axis machine tools, 2008 International Conference
on Smart Manufacturing Application, IEEE, Gyeonggi-do, South
Korea, 2008, pp. 209–213.
Y. Koren, Cross-coupled biaxial computer control for manu­
facturing systems, J. Dyn. Syst. Meas. Control 102 (1980), 265–272(last viewed in 1980).
D.C.H. Yang, T. Kong, Parametric interpolator versus linear
interpolator for precision CNC machining, Comput. Aided Des.
26 (1994), 225–234.

AUTHORS INTRODUCTION
Associate Prof. Chung-Wen Hung

Mr. Shih-Ting Yu

He received the PhD degrees in ElectricalEngineering from National Taiwan
University in 2006. Currently, he is anassociate professor in National Yunlin
University of Science & Technology.
His research interests include IoT, IIoT,
Power Electronics, Motor Control, and AI
Application.

Mr. Yu-Ming Guan

He received the M.S. degrees in electricalengineering from National Yunlin Universityof Science and Technology, Yunlin, Taiwan.
His research interest focus on motor control.

Mr. Wen-Hua Hu
He received the B.S. degree in electricalengineering from National Yunlin
University of Science and Technology,Yunlin, Taiwan in 2018. His current
research interests include motor driver
system and system integration.

He received M.S. degree in MechanicalEngineering from University of Alabama,
Tuscaloosa, USA in 1989. Currently he is
an assistant professor in National Yunlin
University of Science & Technology. His
research interests include Iot, Digital
imagine application product development
and AI application.