Ekomachines (2) – Energy-efficient Drive Technology
Automation and robotics in production would not be possible without drive technology.Drive devices are essential elements of lines and machines. They can be found in a range of industrial processes, such as transporting components on a production line, various types of assembly, mechanical processing, mechanical functional testing, or in various pumping devices, pollution extraction devices, or fans. At a time when electricity prices are not decreasing and reducing the environmental impact of production is a crucial issue in the industry, the energy efficiency of drives and the modernization of processes gain importance.
Where to Find Savings?
According to various sources, electric drives can account for up to 60-70% of industrial electricity consumption. Therefore, there is a lot at stake in terms of energy efficiency and innovation. Estimates are even made about the possible levels of savings, which are difficult to relate to precisely but are in the order of 103 TWh per year. The industry mainly uses electric, pneumatic, or hydraulic drive devices. Ultimately, pneumatic or hydraulic devices are powered by compressors or hydraulic power units, whose essential element is an electric motor. Electric motors themselves also vary depending on their purpose. Permanent magnet (PM) motors can provide more efficient operation in applications with variable speeds than typical asynchronous motors because the efficiency of permanent magnet motors is higher. Among the advantages of PM motors are high torque overload capacity, wide speed range, good regulatory properties, smaller size (compared to induction or DC motors), and increased reliability due to the lack of a brush node. Modern permanent magnet motors are generally divided into two groups: brushless DC motors (BLDC) and synchronous motors (PMSM). It is hard to imagine today’s industrial automation without servo drives. These drives operate in a closed feedback loop system, where the actuating element is an electric motor, and the control element is a controller. Feedback comes from encoders or sensors. The mentioned advantages of servo drives include reduced energy consumption, immediate start-up, dynamic regulation, and size reduction.
Energy-efficient Innovation on the Example of a Shock Absorber Characteristic Tester
In the production process of shock absorbers, functional testing is crucial, which simply means simulating road irregularities and observing the shock absorbers’ response presented as an appropriate characteristic. When attempting to automate the process of testing the damping force characteristics of shock absorbers, it is necessary to use appropriate drives that induce movement to measure the relationship between vibration amplitude and frequency, considering various damping coefficients. Practice shows that most testers cannot simulate movements that reflect the real working conditions of a shock absorber. Additionally, during characteristic testing, the smallest possible measurement error is required, which can be as high as 10% in standard applications. Furthermore, a short cycle time and precise displacement measurement over a wide range are necessary. For proper shock absorber characteristic testing, force measurement with a certain precision is required.
Typical market solutions are based on a hydraulic actuator that moves the shock absorber rod with appropriate force. The design of hydraulic drives has its drawbacks, the main one being the dependence of speed on oil temperature and operating loads. Oil, as the main working medium, is also very sensitive to contamination, which is detrimental to the drive. In principle, the only preventive measure is frequent oil changes, which involve more time-consuming and resource-intensive maintenance. Multiple energy transformations in a hydraulic drive result in lower efficiency compared to electric solutions.
In the CTS workstation – an innovative design by ELPLC S.A. – Siemens electric linear motors were chosen as the drive for the testing actuator. This achieved a compression force (Fmax) of 10350N. The motor was also chosen for its maximum speed (Vmax) reaching 90m/min, which allowed for a shorter testing cycle time. The force measurement is complemented by distance measurement in the unit of time using the IMS-I measurement system by Bosch Rexroth. The measurement error achieved was 1.5%, whereas in hydraulic drive-based solutions, this parameter can be as high as 10%. A cycle time of 6.8 seconds was also achieved – compared to 7.2 seconds for hydraulic drives. Replacing the traditional hydraulic drive brought many benefits: no additional oil supply system, no need to monitor oil temperature, pressure, and consumption, high control dynamics at high power. Changing the drive technology resulted in not only energy savings but also specific operational and quality benefits in the form of shorter cycles and more accurate measurements.
It is worth noting that the tester can also be part of a complete, modular production line for assembling and testing shock absorbers. This solution is ELPLC S.A.’s response to the needs of manufacturers expecting automation of the shock absorber assembly process with autonomous operation, high assembly accuracy and testing, and durability and energy efficiency. The line only requires loading and unloading operations, which can eventually be performed by robots and AGVs.
