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Poclain Hydraulics, Verberie, France, is using LMS Imagine.Lab AMESim software (also called AMESim) from Siemens PLM Software to help design robust hydrostatic systems, such as transmissions for use in heavy duty vehicles. In recent years, automotive suppliers have shifted from providing components to providing complete systems to their original OEM customers. Poclain Hydraulics also has made that transition, implementing new competencies that enable the firm to perform simulation on the full transmission system of its customers’ machines.

The use of AMESim enables Poclain to simulate transmission behavior, helping its engineers develop answers to given issues faster and at a lower cost. “AMESim enables us to imagine new solutions because of a better understanding of the system,” says Gilles Lemaire, Poclain Hydraulics’ scientific support manager. “In particular, the simulation enables us to focus on variables that cannot even be measured, and test new concepts without the need of an expensive prototype. For vehicle simulation, even if we have a good knowledge of each component, the interaction between them is not always easy to evaluate.”

Simulation Helps Manufacturer Improve HST Design, Fig. 1

Poclain chose AMESim for this work because of the diversity of available libraries and the different levels of simulation provided—from detailed hydraulic components to hydraulic systems and complete vehicles. Another factor was the ability to address global system simulation with an explicit representation of components, such as pumps, motors, and valves.

Making a more efficient passenger bus

Take the example of a new vehicle, like a hybrid commercial passenger bus: Poclain Hydraulics initially strives to understand the effectiveness of an existing bus, taking into account the vehicle’s duty cycle, driver, and local traffic laws. The second phase is to study new solutions and analyze their efficiency—not only on the actual duty cycle, but also with respect to the robustness of the solution under different load cases.

Simulation Helps Manufacturer Improve HST Design, Fig. 2

The main issues for the bus project are to how to store the maximum amount of braking energy and how to release it as efficiently as possible. To store the maximum amount of energy, the size of the system must be adequate to the requirements of the driver at any time during the duty cycle, under any condition of use. By grasping the efficiency of each component of the hydraulic system at any phase of use, the simulation enables global efficiency for the energy release. This is not easily measured on an actual vehicle, but readily simulated on computers.

The main contribution of the simulation is to analyze the impact of the system on the fuel consumption of the vehicle, as affected by the main mechanical transmission and the engine. For example, in decreasing the power demand on the engine during restitution phases, the impact on its efficiency was not always positive. “Using the simulation capabilities of AMESim, we were able to estimate the best way to release the stored energy by improving the control of the hydraulic mechanical systems,” says Lemaire. “We also particularly focused on the way the gearbox is controlled during braking to make all of the systems work together. This provides the best experience for the driver, and maximizes energy regeneration.”

Simulation Helps Manufacturer Improve HST Design, Fig. 3

From this analysis, Poclain engineers adapt new components with better efficiencies while choosing the right size of components, keeping in mind the results for various duty cycles. “We end up with a good knowledge of the application, a good understanding of its functionality, and important clues for its improvement,” notes Lemaire. “At a higher level, this experience enables us to analyze a new application, such as ‘duty cycle + vehicle,’ to predict potential energy regeneration solutions.”

“At the same time, we take advantage of the different level of details offered by AMESim in order to investigate transient phases,” adds Yohann Brunel, advanced studies engineer at Poclain. “We are able to study behavior, such as engagement and disengagement of the motors from a complete representation of each motor piston, in order to synchronize them with the wheel speed.”

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