Industry Articles Display
2018-04-10 Control Engineering
Control system benefits on mobile machine include improved machine and equipment performance, quicker production, and easier maintenance.
By: Wade Wessler and Chris Vrettacos, Cross Company
There are several reasons to consider utilizing a control system made specifically for mobile machinery for the latest mobile off-road and on-road control systems.
1. Improved machine and equipment performance
Analog/PWM I/O - more precise control
When controlling a boom with a joystick with on/off valves (bang/bang), the control can be jerky, and the boom can be difficult to maneuver. With a control system, an analog or pulse width modulation (PWM) output can be utilized to a valve and ramp up the speed as more joystick force is applied. This ramping is easily done in software, and can give the user very precise control of the boom.
Ability to automate functions
When operating a machine, typically there are functions that need to be done in sequence. This can be difficult and complex when using relay logic. With a control system, all of these functions can be sequenced very easily with the software. In addition, the wiring is greatly simplified which makes troubleshooting much easier.
Advanced diagnostics = less downtime
By designing diagnostic screens to fit the machine design, troubleshooting can be much easier than with relay logic. These screens can include things like input/output (I/O) output status, and short circuit, and wire break detection on field components. This allows the user to find the issue quickly, resolve it, and get back to work.
Ability to save "recipes"/configurations
There are times when there are multiple operators running a machine. One operator might like his machine set up one way, while another likes it set up much different. A simple example of this is the seat position in your car. With a control system, you can do something very similar with the set-up of a machine. These "recipes" can be saved for other operators operating this same machine. No more fine-tuning of the machine every time you jump into the cab to get some work done.
Custom operator interface
These operator displays can be tailored to a specific machine with specific needs. In addition, these provide the method for getting diagnostic information from the vehicle. With the newest displays on the market, these operator interfaces can store wiring schematics, pdf manuals, and with the new feature of being able to play videos, users can have access to videos showing "how to" fix high maintenance items.
Customize component input devices
For more gradual control (ramping), an item such as a joystick can be custom configured. We can manipulate joystick response curves and instead of them being linear, we can change the curve to be less responsive until more joystick "force" is applied. For example, this can make boom movements less "touchy," and give precise control over how the machine functions.
For improved machine performance, and identifying when a machine is being operated outside of its design parameters, data logging can be implemented with control systems. When different events happen, such as operating the machine without the proper oil pressure, or at too high a temperature, these all can be logged in the memory of either the display or controller. This information can then be downloaded to some type of portable memory device which allows this to be analyzed. Not only is this valuable for the service department and warranty claims, but this can be used in the design stage of a machine.
Potential for remote monitoring
With the use of CAN-based control systems, a mobile machine can be monitored remotely. This includes downloading software updates, retrieving data logs remotely, disabling a machine operating outside of a given geography (geo-fencing), or just real-time monitoring. This can help limit service expenses as the user monitors a machine in real-time from the office.
2. Easier, quicker production and start-up
Reduce and simplify wiring
Through the use of CANbus communications, the wiring is drastically simplified with a control system. This includes the wiring to the electronic engine, field devices such as valves and I/O blocks, and with the HMI operator display. Users no longer have to run individual wires out to devices, all of the devices can be distributed throughout the machine and connected via CANbus.
Pre-configured controllers and human-machine interfaces (HMIs)
Controllers and operator interfaces can be supplied with programs already preloaded so there is no configuring or downloading of software. Once the proper connections are provided, the user is ready to go.
I/O feedback to check/verify wiring
As a part of the machine diagnostics, I/O feedback can be provided. This allows the user to verify the wiring is correct during production and start-up. No more getting the machine out in the field only to find out a component is miswired in production.
Potential for "self-calibration"
Sometimes the theoretical machine operation (what was designed) doesn't match the actual machine operation. With a control system, machine outputs can be automatically set based on the "actual" machine operation. Also, each machine is a bit different in how the outputs respond. These can be easily "tuned" using a control system so each machine reacts the same.
3. Engine and transmission controls
J1939 feedback, throttle control When using a relay system, there is no way to communicate with modern electronic engines. Using a CANbus control system, this is done via the J1939 CANbus protocol. An example of this is being to manipulate or put limits on the speed of the engine through the control system. Because the transmission also uses this same communication protocol, the user can monitor and get feedback from the transmission.
Modern electronic engines provide messages to inform the user about their status, how they are operating, what conditions they are seeing, and if there are faults. All of these messages are provided via CANbus. These messages can be captured and stored using a control system.
Tier 4 integration
Tier 4 represents the current emission requirement for diesel engines above 25Hp. These engines use different methods for meeting emission requirements, and all of them are electronic engines that can only be monitored by controls communicating via CANbus.
Because a control system can communicate with the engine and transmission using CANbus communications, if an operation on the machine causes the engine to "bog" down, the user can easily change the operating conditions to prevent the engine from stalling. An example would be if the user hit something with the brush cutter. The control system could automatically monitor the machine and increase RPM to a certain point to overcome this bind, and if need be, automatically disengage the cutter motor. This would be very difficult to do with relay logic controlling the machine.
4. Easier to maintain and upgrade
Machine function changes are easier via software revisions
Let's say a machine is deployed in the field and the customer realizes the operators like to run the machine at a lower speed for more control. This can easily be done by limiting the maximum RPM the engine can be run at. A simple setpoint change can be done through the HMI used to limit the RPM.
Adding components is easier than having to "hard-wire" with relay logic
Adding components on a mobile machine control system with CANbus is very simple. This can be done by easily adding a component to an existing CAN I/O module and a change in the logic of the controller. If no CAN I/O module is available, one can be added for low cost and a minimal amount of wiring (4 wires).
Wade Wessler is the Cross Company mobile controls product manager. Chris Vrettacos is a Cross Company controls engineer. This article originally appeared on Cross Company's Mobile Hydraulics & Controls' blog. Cross Company is a CFE Media content partner. Edited by Chris Vavra, production editor, Control Engineering, CFE Media, email@example.com.