The Design of Human-Machine Interaction System for Rapier Based on Linux

1. The Design of Human-Machine Interaction System for Rapier
Based on Linux
Lili Huang1
, Hejin Liu2
, Antao Chang2
, Guodong Li2
, Qunmin Wu2
, Senlin Zhang1
1. College of Electrical Engineering, Zhejiang University, Hangzhou, China
2. Hangzhou Wumu Technologies Company Limited, Hangzhou, China
llhuang@zju.edu.cn, liuhejing@netease.com, antaochang@126.com, qunmin_jingweihz@163.com,
hdguodong2000@163.com, slzhang@zju.edu.cn
Abstract—For the purpose of better experience of interaction,
high efficiency of communication and better scalability, a new
kind of human-machine interaction system for rapier based on
ARM-Linux was proposed in the article. It was chosen
customized Linux embedded platform on which ARM9 is the
processor to design the system. According to the rapier’s
functional requirements, Qt4 framework was used to design
the interface. Meanwhile, in order to overcome the limitation
brought by driver based on character device, Socket-CAN
driver which is based on the networking device was used to
complete the message transmission. A large number of test
results indicated that the system designed has good ability of
interaction, characteristics of stable operation, high reliability
of data transmission, easy maintenance and expansion.
Key word- human-machine interaction; embedded Linux;
Socket-CAN drivers; modern loom machine
I. INTRODUCTION
On a rapier, the human-machine interaction system
meets the interaction like inputting parameters and
displaying working status between operator and machine
by using the interface. The design of the system contains
hardware design, Linux operation system customization,
interface design, data transmission and so on. As our
economic development mode transforming, it requires
urgently to develop and apply advanced technologies,
devices to improve the quality and technical value. The
human-machine interaction system of traditional loom
machine was used to be designed based on 8 bits or 16 bits
chips. They can only realize limited function and have
poor scalability, and the interface can’t meet the
interaction well enough. Nowadays, some world famous
loom companies have made modern machines with faster
response and more intelligent interaction system by using
platform like 32 bits embedded system. But rapiers made
in our country are most low grade products, so it’s
necessary to design more intelligent human-machine
interaction system for rapier. In this paper, we complete
our interaction design with 32 bits embedded system.
II. SYSTEM STRUCTURE
The hardware of human-machine interaction system
consists of ARM (AT91SAM9261) core module, CAN
module, USB module, Ethernet module, touch screen and
LCD display module, power supply module. The
AT91SAM9261 is a complete system-on-chip built around
the ARM926EJ-S ARM Thumb processor with extended
DSP instruction set and Jazelle Java accelerator. It
connects the CAN controller through SPI bus. The USB
module is used to copy files between rapier and computers,
it also will be used to connect keyboard when debugging
or upgrading. A network can be built between rapiers
through extended Ethernet ports, thus we can realize
centralized control of them. The LCD with touch screen
can do inputting and displaying conveniently. Using
customized Linux as the operating system to manage the
hardware resources uniformly. Fig 1 shows architecture of
the design.
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978-1-4673-6278-8/13/$31.00 ©2013 IEEE
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2. Human-computer interface CAN
communication
module
Application layer
Kernel(including CAN
protocol family)
Linux OS layer
CAN drivers
AT91SAM9261
MPU
USB
LCD
Network
Touch screen
Flash SDRAM
CAN
controller
CAN
transceiver
Hardware layer
Data bus
Figure 1. Architecture of human-machine interaction system
III. CAN-BUS REALIZATION IN
ARM-LINUX ENVIRONMENT
In a rapier system, the other modules such as let-off
system are already extended with CAN control ports. The
CAN protocol is standardized in OSI model which
consists of data link layer, physical layer and application
layer. The controller implements the completion of the
protocol, and the transceiver converts the logic level
signals into the physical levels on the bus and vice versa.
A. The Hardware Design of CAN-Bus
The AT91SAM9261 module is extended with 64M
bytes SDRAM and 256M NAND Flash. Choosing
MCP2515 as the CAN controller, it is capable of
transmitting and receiving both standard and extended
data and remote frames. The MCP2515 interfaces with
MCU via Serial Peripheral Interface (SPI). For the
purpose of improving system reliability and noise
immunity, we connect high-speed
optocouplers-HCPL0600 between the controller and
transceiver.
B. The Design of Drivers of CAN-Bus Based on
ARM-Linux
The Linux way of looking at devices distinguishes
between three fundamental device types: char module,
block module, and network module. Each module usually
implements one of these types.
Before Socket-CAN [1], CAN implementations for
Linux is often based on character devices. Socket-CAN
uses the Berkeley socket API, the Linux network stack
and implements the CAN derives as network interface. It
overcomes some limitation brought by character device
implementations, like: Change of CAN hardware vendor
need to adapt the CAN application; complex filtering have
to be implemented in the applications in user space. In
Socket-CAN implementation, CAN frames from the
controller can be passed up to the networking layer and on
to the CAN protocol family modules, including the raw
socket protocol and the broadcast manager, and vice versa.
So it can use all of the provided queuing function in the
Linux networking layer.
Application
Application
Protocol
User space
Socket
CAN
protocol
family
Internet
protocol
family
Networking driver
Character
driver
kernel space
CAN controller CAN controller
Hardware space
Figure 2. Comparison of two kinds of driver
So the implementation of Socket-CAN consists of
two parts: A protocol family PF_CAN and the driver for
CAN networking devices. The new protocol family
PF_CAN transmits the frames in the networking layer and
provides useful user space utilities. The driver’s function
can be described as follows: Initializing and configuring
the hardware; pushing the incoming CAN frames from the
buffer of MCP2515 to the buffer of the upper layer;
transmitting the outgoing frames from the upper layer to
the bus. When the driver is loaded, the kernel calls the
driver’s “probe ()” function. This function performs the
basic initialization including arranging address ranges,
requesting IRQ numbers and configuring SPI function. By
calling “register_netdev ()” function, the device is
registered at the networking subsystem in the kernel.
Receive path: When arriving at the CAN controller,
the incoming message is stored in the receiving buffer of
MCP2515. Then an interrupt is aroused automatically.
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3. Interrupt handler stores a notification into “softnet_data”
queue and the message is read from the controller later.
NET_RX_SOFTIRQ is called to place the frame into
corresponding skb_queue.
Transmit path: Sending messages is originated in the
user space. When an application wants to send raw CAN
frames, a CAN_RAW socket is opened and “send ()”
system call is issued. The protocol copies the CAN frame
into the kernel space and passes it to the packet scheduler.
After that, the message transforms to CAN frame by
calling “MCP2515_hw_tx ()” and write it to the CAN
controller’s TX buffer by calling
“MCP2515_hard_start_xmit ()” through SPI and the
message will be sent onto the bus.
CAN
contoller
IRQ
handler
Soft net_data
queue
Net_rx soft
IRQ
Skb_queue Applicaton
CAN message
IRQ skb
Figure 3. Socket-CAN RX path
C. Compiling and Loading the Driver of CAN-Bus
There are two ways to make the driver working. The
first is compiling the driver into the kernel statically. The
other is making it as a module so that we can just need to
load it when using it. We take the second way during our
design because it can save memory and make the
debugging conveniently. When generating CAN driver
module, firstly, we have to point out the route of
cross-compile chain in the file of “Makefile” on the host.
Secondly, it’s necessary to let the compiler know that our
target is ARM and our chain is “arm-linux-”. After
executing command of “make”, a file tailed with “.ko”
will be generated. The last job is to copy the file to the file
system of the target, and execute “insmod”.
IV. DESIGN OF THE INTERFACE AND
COMPLETATION OF THE DATA
INTERACTION
A. Design of the Human-Machine Interface
Qt is a cross-platform application framework that is
widely used for developing application software with a
graphical user interface. Because of its object-oriented
programming, large quantity of documents and abundant
of API for programming, we use Qt to design the interface,
too. Qt/Embedded is a version used for embedded system
which uses the same Qt libraries and API. So the interface
can be designed on the host and then cross-compile the
project to run on the target. The Qt libraries should be
transplanted onto the ARM first.
The function of the interface contains: Input operating
parameters like angles of reading the tension before turn
on the rapier; display some information when loom is
working, like warp tension, rapier’s speed; deal with some
counting such as stopping times, the length of weaved
cloth; display warning messages when loom shuts down
accidently. Some functions contained in the system are
shown in Fig 4.
User login
Parameter
setting
Data access
Data setting
Status
display
Hardware
testing
Running data
Weft choosing
Warp setting
Coiling setting
status
Warning message
Work shift
Date and time
CAN bus testing
Air break testing
Motor setting
Stop angle
Sensor setting
Weft feeder
Weft unit
stops
Stop angle
Speed
tension
Cloth length
Writting INI
Reading INI
.
.
.
File
invokeing
Figure 4. parameter scheme of HMI
In Fig 4, the function of files’ invocation contains
flower tissue’s copying and using, storage and
management. We can copy tissues from external
computers via USB port. All of the tissues stored in the
system will be shown by using list view. The system
carries along with the function of editing tissues of Dobby.
Soft keyboard is used to input data. When a inputting
edit-line gets the focus, the soft keyboard will eject
immediately. And every time before turns up, the position
will be update closely to the inputting area. The inputting
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4. data will be stored in the form of INI by using the class
-“QSettings”.
In order to prevent error inputting or operating, we use
“QRegExp” class and regular expressions to limit the
range of inputting. We also designed necessary dialog
boxes to note the users whether they can do it or they will
do it. All these measures can enhance the reliability of the
system.
When power on, the system will detect other modules.
If any of them doesn’t work normally, the interface will
give a message about the error. Even when the loom stops
working accidently, the interface will also show warning
message. In this way, the workers can fix the loom up
quickly according to the point. The interface is designed
like Fig 5.
Status of rapier
Parameter setting
running
parameters
Weaved
cloth
Shift and
efficiency
Figure 5. The main interface
B. Data Interaction
In order to transmit messages among CAN nodes,
CAN program should be completed in application. Since
Socket-CAN protocol has provided interface for user
space programming based on network, we just need to call
“socket ()” function to open a socket. The socket uses the
protocol family-PF_CAN which including CAN_RAW
and CAN_BCM for broadcasting. Then bind the socket
with CAN device and call “write ()” to send the message
after finishing writing the frame. Or call “read ()” function
to get the message on the bus.
To ensure the screen real-time response to user’s
operation, we use multi-thread programming method. One
of the sub threads is dealing with data receiving
exclusively. Once a sub thread is created, it is blocked
until an appropriate event happened. So the processor has
enough time to deal with other tasks.
C. CAN Communication Protocol
We custom the CAN communication protocol and
configure the MCP2515 working on the Peli-CAN mode.
Messages are transmitted via extended frame format
which consists of 1 byte for frame information, 4 identifier
bytes, and up to 8 data bytes. Since a frame has higher
priority when it has smaller ID, different frame types are
defined. ID13-ID16 is used to distinguish the warning
message, command message, broadcast frame,
multi-frame etc.
ID28 ID27 ID26 ID25 ID24 ID23 ID22 ID21 ID20 ID19
Frame type
Source address
ID18 ID17
ID16 ID15 ID14 ID13 ID12 ID11 ID10 ID9
Destination address
reserved
ID8 ID7 ID6 ID5
ID4 ID3 ID2 ID1 ID0
Functional code
Functional code
Figure 6. Definition of frame ID
V. CONCLUSIONS
The human-machine interaction system is a key node
of rapier control system. The interface designed based on
embedded Linux has good portability and scalability. It’s
also easy to be maintained and upgraded. By using Qt4
framework, color LCD with extended TFT format and
touch screen, the interaction between operator and
machine is convenient. Modular design method,
reasonable controls’ layout and better fault tolerance make
the interface more humanity. Using multi-thread
technology ensures that the response is quick enough. In
practice, the system communicates with other CAN nodes
in speed of 250kbps. The result proves that it works stably
and data transmit correctly. This work can be useful for
designing modern loom machine.
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5. REFERENCE
[1] “The SocketCAN project websites,”
http://developer.berlios.de/projects/socketcan.
[2] Su Rongyan, Chang Jiupeng, and Shao Liqing, Deng
Kangyao, “Design of Test Control System Interface
Communication Card in Engine Based on CAN Bus,”
Micro Computer Information, 2005,1,101 - 103.
[3] Li Dinggen, Chen Jun, and Wu Zhaohui, “Research and
development of in-vehicle information platform based on
Arm-Linux ,” Journal of Zhejiang University (Engineering
Science), Vol.40, Sep.2006.
[4] Wang Hongkai, and Zhang Senlin, “Design of the software
system of automaitc flat knitting machine based on Linux
embedded technology,” Journal of Textile Research,
Vol.29, Feb.2008.
[5] T. Nolte, M. Nolin, and H. Hansson, “Real-time
server-based communication for CAN,” IEEE Transactions
on Industrial Informatics, Vol.1(3), pp.192 - 201, 2005.
[6] Zhao Bing, “Roving frame control system based on CAN
bus,” Journey of Textile Research, 2006, Vol.27(5), pp.84 -
86.
2004