Test bench and laboratory systems play a crucial role in product development, validation, durability testing and lifecycle testing. These systems vary in size and complexity, many relying on linear actuators to apply controlled motion or load to a device under test.

Test engineers often face a different set of constraints than engineers designing production equipment. Test bench availability may be limited, development schedules can be aggressive, capital budgets may be tight, and a single system may need to accommodate multiple products or test profiles.

Once testing begins, the system may also be expected to cycle continuously for weeks or months while generating and logging consistent, reliable data.

These realities make the actuation system an important part of overall test system design. Reliability, flexibility, data acquisition, implementation time and operating cost should be considered alongside force, speed, stroke, duty cycle, and control requirements when evaluating hydraulic, electromechanical or hybrid actuation technologies.

6 Key Factors That Dictate Test System Designs

When developing a test system and choosing the actuation technology to utilize within it, there are six important design aspects that must be taken into account.

1. Minimizing Downtime and Maximizing Test Availability

4. Evaluating the Capital Investment

Budget constraints and capital justification can also influence test system design. When evaluating actuation technologies, comparing the initial cost of the actuator alone may not provide an accurate picture of the total investment.

Each actuation technology has different system requirements that can affect both the initial investment as well as long-term operating costs. Beyond the actuator itself, engineers need to account for power consumption, controls, feedback, plumbing or cabling, maintenance and other supporting components depending on the technology selected. Ongoing expenses that should also be considered include energy consumption, maintenance, and system upkeep.

5. Reducing Engineering and Implementation Time

The development of test systems is often tied to product development schedules, making the time needed to get a test stand operational an important consideration. Engineers might need to design, assemble, program, and validate the system within a limited timeframe.

The actuation technology selected can influence how much engineering is required to get the system running as engineers may have to size and integrate motors, drives, sensors, controls, program the required test sequences, etc.

A more integrated actuation solution can reduce this burden by providing a system where the components are already sized and designed to work together. Actuation systems that can be supplied assembled, programmed, and tested can also shorten the path from selection to an operational test bench.

6. Managing Energy and Operating Costs

Some test systems operate intermittently, others like lifecycle, fatigue, and durability test stands may run continuously for weeks or even months. For systems running this frequency, energy use and heat generation can have significant impact on operating costs.

Energy consumption can vary significantly depending on the actuation technology, so it should be evaluated across the complete test cycle.

Engineers should consider how much power is required during periods of actuation, loading and holding, as well as any additional energy or cooling required to manage heat generated by the system. Operator comfort and ergonomics within the test lab should also be considered when evaluating the overall system design.

Important Considerations When Selecting Actuation Technology

When it comes time to choose between a hydraulic, electromechanical or hybrid actuator for a test system, the following aspects should be considered.

Evaluate the Complete Test Profile

Force, speed, and stroke requirements can change throughout a test cycle. A test may require higher speed while approaching the device under test, higher force at a lower speed during loading, a controlled hold period and a different speed during return. Looking at only the peak requirements can leave out important parts of how the actuator will actually operate during the test.

Duty cycle and expected life are also important factors, especially for endurance and lifecycle testing. A system operating a few times per day has very different requirements than one cycling continuously for weeks or months. How often the actuator cycles, how long it operates under load and the total number of expected cycles should all factor into actuator selection.

Consider Control and Loading Requirements

Test systems require different levels of control depending on the application. Some applications may only need point-to-point positioning, others may need precise control of position, speed, or force throughout the test. Requirements may also include needing the system to move to a specific position and then transition to applying or holding a defined force.

Certain applications such as destructive testing and accelerated lifecycle testing can place excessive stress on actuators. Depending on the test, the actuator may experience shock loading or side loading. These conditions affect actuation technologies differently and should be considered early in the design process.

Feedback also plays an important role in both control and repeatability. Engineers should consider what needs to be controlled and measured, how quickly the system needs to respond to changing conditions, and how that information will be communicated to the test system.

Consider the Test Environment and Existing Equipment

Where the test system will operate can also impact technology selection. Available space, noise, heat, cleanliness, maintenance access, and available electrical or hydraulic infrastructure may all factor into the decision.

For environmental or durability testing, engineers might want to consider harsh operating conditions, explosion proof, shock, and vibration.

With a new system, the actuation technology can be considered as part of the overall mechanical and controls design. For an existing test stand, it may make more sense to keep cylinders, fixtures or other components that are still working and update only the portions of the system that need to change.

Comparing Actuation Technologies for Test Applications

Once the requirements of the test are defined, engineers can compare the different actuation technologies and determine which makes the most sense for their application.

Traditional Hydraulic Actuation

Traditional hydraulic systems are commonly used for testing applications that require high force and the ability to handle shock or externally applied loads. They can also make sense when hydraulic infrastructure is already in place.

The complete hydraulic system should be considered when evaluating this approach. Traditional hydraulic systems include the cylinder, a hydraulic power unit, reservoir, filtration, valves, hoses, piping and cooling. Noise, heat, fluid management, maintenance, flexibility, and available floor space can also be considerations, especially in laboratory environments.

For applications requiring more precise motion or force control, proportional or servo valves and feedback can be incorporated into the hydraulic system.

Electromechanical Actuation

Electromechanical actuators provide programmable motion without the need for hydraulic power or plumbing and can be a good fit for many test bench and laboratory applications.

When evaluating an electromechanical actuator, engineers should look at the combination of force, speed, stroke and duty cycle required by the test. Gear/screw backlash, shock and side loading should also be considered, particularly for demanding durability or lifecycle testing, as these loads negatively affect the mechanical components within the actuator.

Hybrid Actuation