Wednesday, November 16, 2022 · 16 min read
Upgrading Pratt Miller’s Test Bench Controls with Dewesoft’s IOLITE System
When your team depends on the reliability and serviceability of your test bench, Dewesoft’s IOLITE real-time DAQ and Control hardware provides a robust and flexible solution. This certainly was the case with Pratt Miller Engineering and their hydraulic test stand, who upgraded their test bench with IOLITE.
Pratt Miller Engineering (formerly Pratt & Miller Engineering), is based in New Hudson, Michigan. They are known for their extremely successful Corvette Racing program, having won five IMSA SportsCar Championships and eight 24 Hours of Le Mans victories.
The company delivers innovative products not only in motorsports but also in the defence and mobility industries. Pratt Miller’s test and development department play a key role in the company’s success. They validate and refine the company’s innovative technology, always striving for engineering excellence. Their test benches must be powerful, flexible and reliable in order to accommodate the wide array of testing required.
When their large hydraulic power unit and flow bench’s control system began to show their age, it became clear an upgrade was needed. The test bench computer running Windows 7 and obsolete controls hardware was becoming unreliable and difficult to service. Pratt Miller engineers began searching for a retrofit fit option that wouldn’t require hiring system integrators or costly in-house development of a custom control system.
Dewesoft’s IOLITE system became the obvious choice given Pratt Miller’s extensive experience with Dewesoft’s lineup of software and hardware. IOLITE provided a scalable and powerful test bench controller and real-time DAQ system all in one. With it, they could control hydraulic power, and it could be interfaced easily with relays, programmable power supplies, and even third-party controllers via its analog out, digital out, and EtherCAT outputs. IOLITE’s flexibility would allow it to keep pace with Pratt Miller’s increasingly busy test and development department.
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Controller hardware development
IOLITE has slots for a variety of input and output modules. A large array of modules are available, including strain gages, thermocouples, RTDs, voltage I/O and digital out modules. Pratt Miller needed the system to control high-current servo valves, high-current proportional valves, and self-powered proportional valves. These valves are necessary for controlling and regulating test fluid flow and pressure.
Interfacing with the high-current servo valves required the use of an external power supply to provide power and solid-state direct current (DC) relays capable of being switched with the IOLITE analog out of the channel. These DC relays were interfaced with the IOLITE analog out of the channel and controlled via a 5 VDC signal.
Controlling the high current proportional valves required a more creative solution. The analog out module can provide 0 to 10 VDC up to 20 mA. The proportional solenoid requires 24 VDC, so a programmable power supply was used that accepts 0-10 VDC and outputs 0 to 2.5 ADC at 24 VDC.
For proportional valves with integrated power supplies, IOLITE’s AO (analog out) module can provide the ±10 VDC signal necessary to directly control the valve position. These kinds of valves can be connected directly to the IOLITE AO module without the need for any external power supply.
In addition to control, the IOLITE system also had to read signals from a variety of sensors on the test bench, including flow meters, thermocouples and pressure sensors.
Normally such a variety of sensors would require different modules, but IOLITE’s STG module can read differential voltage, current, and a variety of strain gage/bridge inputs. The pressure sensors output a differential 0 to 5 V signal. The STG module is the best choice because it can handle all of these sensors, and is even compatible with the DSUB-9 connectors that Pratt Miller was already using for these sensors.
RTD and thermocouple modules were selected to allow maximum flexibility in temperature measurements. System temperature and test article temperature could be monitored simultaneously.
IOLITE’s dual-counter (CNT) module was selected to measure direction and volume from a flowmeter. Separate magnetic pickups detect flow direction and volume, and both can be connected to a single CNT input. With a few selections in the software, the counters can be configured in the software according to the manufacturer’s datasheet.
Pratt Miller selected the IOLITE R12 chassis so that they could mount the system inside a standard 19” server rack. All hardware, including relays, power supplies, and computers, can be contained within a single protective enclosure. The R12 also has extra I/O module slots so that Pratt Miller engineers can add more channels in the future.
Controller software development
DewesoftX is a powerful control software that makes I/O setup and system configuration highly flexible and graphical. A built-in math module provides a closed-loop PID control for proportional devices as well as digital control for servo valve devices. User inputs are provided in the form of graphical input boxes, drop-downs, buttons, and switches that control various test bench parameters.
Using the built-in math module, it is possible to set up several types of controls and virtually any kind of calculation. Engineers can write simple “IF” statements to control the temperature of the test fluid, and the state of the system, and to specify the conditions for an automated emergency stop. Math functions run in real time, but they can also be added and calculated after a test to provide further analysis.
The signal play plugin
In addition to all of its built-in functions, DewesoftX’s capabilities can be extended with custom software plugins. Pratt Miller needed their test bench to be able to import predefined profiles and write them to specific channels. A plugin called Signal Play was written to allow users to import a profile from outside software and send that profile to a control channel as a wanted value.
The Signal Play plugin allows the user to select a maximum sequence length, which corresponds to how many profiles a user can run sequentially. It is possible to upload and save multiple sequences at a time, all of which are stored within the setup file, and can be accessed at any time. Multiple instances of Signal Play can be run at the same time, allowing the plugin to be used to control different parameters across multiple channels.
Customizable displays for every test
Due to the variety of work that Pratt Miller performs, every test is different, and operators need to view and store different parameters. The DewesoftX user interface is completely customizable to suit every user and application. For the hydraulic control interface, a standard interface allows the test bench to be operated on a “walk-up “ basis. Users can develop their own interfaces, with any required controls and data displays designed for each test. Users can even develop their own plugins via C++, allowing for endless customization within DewesoftX.
The Signal Play plugin can run sequences either as step inputs or as interpolated points. If desired, a delay between each sequence can be defined as well. To run the sequences, the user simply selects START. If the sequence needs to be halted for any reason, the user can select STOP. Or they can select PAUSE at any time, and resume when they are ready.
Displays can be created for every application, including the tuning of PIDs within DewesoftX. These displays allow for the live tuning of PID controllers using live data from the asset being tuned. Thanks to the nature of the PID controls within the math channels, the values for Kp, Ki, and Kd can be modified via user inputs.
Summary and conclusion
Pratt Miller Engineering is a technology company that prides itself on innovative engineering and product development. Their roots in motorsports are just the tip of the iceberg. Their expertise in robotics, technology integration, platform development, and advanced concepts allows the company to solve complex problems on schedule and within budget.
Dewesoft’s IOLITE system is a powerful upgrade to Pratt Miller’s previous test bench controller. Integrating seamlessly with their existing ecosystem of Dewesoft hardware, the new IOLITE system can expand as new requirements come along, allowing new features and capabilities to be added.
For anyone developing a new real-time controller and DAQ system for a test stand, or who might want to upgrade an ageing system, Dewesoft’s IOLITE provides a flexible and robust solution. IOLITE provides a wide array of I/O modules for recording virtually all signals and controlling valves and relays. This seamless combination of Dewesoft hardware and software is the ultimate tool for today’s test engineer.