Building tomorrow’s construction industry through electrification

e-motec
July 26, 2022

Building tomorrow’s construction industry through electrification

Antti Väyrynen

Industry action and technology leadership are needed to address the climate crisis. With governments and industries moving towards net-zero emissions, the focus on electrifying mobile machinery is growing.

Technology providers can lead the way in creating a cleaner, more sustainable future by developing innovative solutions. This requires a deep understanding of the applications and challenges OEMs face when electrifying their machines.

The electrification business case

While electrification primarily reduces carbon emissions, its benefits cover the entire value chain. While much focus has involved zero-emissions vehicles, hybrids are needed in applications where current technology capabilities do not allow total electrification.

To guarantee a successful electrification transition, electric vehicles must provide enough value over their lifetimes to justify the upfront capital needed to purchase and establish the infrastructure that supports an electrified fleet. For off-highway vehicles, the use case must also consider the application, duty cycles, access to charging and the possibility of grid connection. With few industry regulations driving electrification in the off-highway market, OEMs must provide strong business case evidence.

POC eWheel Loader System Architecture

Rethinking system design

The market’s shift towards zero-emission vehicles powered by batteries and fuel cells has forced manufacturers to change their system design approach. Designing a vehicle is a complex process that requires front-end planning, a deep understanding of the market and the end user’s expectations to choose when to utilize electrification. Over the past decades, market needs have remained relatively stable and have been met with diesel-hydraulic systems. As electrification builds momentum, OEMs are being challenged to incorporate its benefits into their design while still meeting or exceeding user expectations. To meet these demands, intimate knowledge of the operator’s tasks must be paired with the right components and system control.

Timeline, budget and customer commitments also need to be considered when defining the scope and project goals. OEMs should ask themselves: what are we trying to bring to market? Will this vehicle be more of a concept design, or is it intended for production? What sort of customer experience are we trying to create? Will our design improve performance, or are we just trying to get to zero emissions without focusing on full-system optimization?

While concentrating on full system optimization seems like an obvious choice, it requires large investments from OEMs into appropriate resources. An entirely new set of skills and knowledge are needed to understand electric components and how to integrate them. This kind of internal investment is only possible from large OEMs, while the rest of the market must rely on technology providers.

Disassembly of original vehicle to the chassis (top left), component layout used in machine (top right) and the components installed on the wheel loader (bottom left)

Because of Danfoss’ history in mobile hydraulics, its products and tools have evolved based on user expectations and performance requirements. Although experience in electrification is crucial, many other engineering functions require new knowledge on how to apply their technologies to build electric systems. In each of Danfoss’ electrification projects, resources are pulled from different business units to support these developments, with the value gained passed directly to customers.

With an extensive portfolio of electric machines and power electronics, Danfoss’ Editron division have developed products covering a wide range of vehicle sizes, subsystem applications and powertrain architectures. The division has invested in several proof-of-concept machines, the first being a 14-ton fully electric wheel loader located at the company’s Application Development Center (ADC) in Denmark.

Wheel loaders are a common application, with high volumes produced every year. By advancing their design and system architecture, Danfoss aims to create a replicable solution that can be scaled in the market and provide the largest net benefit from electrifying.

PCO Wheel Loader at our ADC's Gravel

From diesel to electric: converting a wheel loader

Developing proof-of-concept machines means that platforms can be replicated, performance levels of diesel counterparts be met or exceeded, and user expectations be fulfilled.

The main objective of Danfoss’ electric wheel loader project was to improve overall performance, which led the team to rethink the entire system architecture rather than perform an engine swap. Through extensive research, engineers concluded that the two-motor configuration would provide optimal efficiency and control. While splitting the propel and work function between two motors predicted significant efficiency improvements, adding more components created separate challenges around the layout and footprint within the chassis and increased vehicle control complexity.

The team started by disassembling a CAT 926M wheel loader, stripping it of almost all internal components until there was little more than an empty chassis to build from. Before starting the dimensioning of subsystems, performance goals were set to direct the team on how to size the different components. Once the objectives were set, the team began sizing the different propel, work function, cooling, and power management subsystems. Once the systems had been studied and dimensioned properly, components were selected and installed in the machine. Because the team was designing from a pre-existing vehicle chassis, the available space within the wheel loader was limited.

After installing the components, testing, tuning and validating the system became the primary challenge. By developing the vehicle at the Application Development Center, the Danfoss team had access to the right tools and testing environments needed to ensure the wheel loader’s performance. The ADC possesses a test track with graded inclines, gravel pits and other features, enabling engineers to test the vehicle in real-life conditions. The team also used advanced simulation tools to test and run software from a desktop computer with an Xbox controller.

Torque vs. Speed for WL Propel System

Hardware overview

The Editron division’s motors and inverters drive the propel and work functions, while DC-DC converters and LCL filters are used for power management. The separation of the propel and hydraulic work functions significantly impacts the dimensioning of the subsystems.

The wheel loader’s propel function consists of a single EM-PMI375-T800 motor with two EC-C1200-450 inverters driving it. The motor connects to a two-speed gearbox, while a transfer case directs torque to either the front or rear axle. The sizing of the propel motor was based on vehicle parameters, such as the machine mass, maximum speed goals, tire size and gearbox ratios.

The wheel loader’s hydraulic work function uses a Danfoss EM-PMI240-T180 motor and EC-C1200 inverter to drive a Danfoss Series 45 hydraulic pump. By decoupling the work function from the propel system, the input speed to the pump is independent of the propel and can be controlled variably to reduce power consumption and optimize efficiency. Additionally, the electric motor can adjust and reach speed quicker than a diesel engine, which increases the loader’s boom response and facilitates operation. When selecting the hardware, the pump’s input speed and displacement dictate which motor and pump selection best fits the application’s requirements.

Hydraulic Pump & E-Motor Curves for Work Functioning System

The overall power distribution of the system is managed by various power electronic components from Editron’s portfolio. These components are needed to direct power to and from the two onboard batteries and the grid connection used for charging. The wheel loader’s main energy storage consists of an 800V battery and a 24V battery for auxiliary functions. The EC-IDC24 DC-DC converter is used to adjust voltage levels between the 24V battery and the rest of the system, while the EC-C1200-450 converter and EC-LCL1200 filter connect to the grid to manage the main battery’s charging.

In addition to the components used to electrify the wheel loader, the displays, joysticks, pedals and software controllers all come from Danfoss Power Solutions. By combining hardware with the software developed and managed by Danfoss’ PLUS+1 tools, the company can support the next generation of electrified solutions in the off-highway sector.

PLUS+1 GUIDE User Interface

Software overview

With the latest advancements in electronic controls in both hardware and software, today’s machines in the off-highway market have become increasingly more complicated and advanced. Developing and controlling them requires extensive software development and tools to support the vehicle throughout its lifetime. Over the past decade, Danfoss has invested heavily into building its PLUS+1® platform to support the software needs of OEMs and system integrators. The PLUS+1® ecosystem acts as a fully integrated development environment with tools that aids all stages of the design cycle, giving customers access to the types of tools and solutions that improve their capabilities, increase design versatility and reduce time to market.

When developing and implementing software onto the e-wheel loader, the Danfoss team used existing software blocks and libraries related to hydrostatic systems. By having access to pre-developed code, the team could apply existing control methods and quickly discover what was needed to control the system’s electric inverters and motors. Although new control algorithms and processes had to be developed, the legacy knowledge of vehicle control and expected performance provided a big advantage to the engineers. Furthermore, because the components are compliant with PLUS+1®, the plug-and-play approach allowed them to switch out various parts and easily configure them within the software.

“By separating the vehicle’s subsystems and focusing on full system optimization, our team could meet the goals for vehicle operating time by lowering overall energy consumption,” explained Antti Väyrynen, off-highway director of Danfoss’ Editron division. “In a traditional diesel configuration, the hydrostatic propel and work functions are driven by the same motor and input speed. However, separating the two systems allows for independent control, meaning the speed of the hydraulic pump can be lowered when not in use to reduce idle losses. As a result, our team calculated more than a 50% reduction in energy consumed by the hydraulic pump, which proved to be one of the biggest contributors to the system’s overall efficiency.”

By facing similar electrification challenges as its customers, Danfoss is building expertise and improving its proficiency in electrification, hydrostatics, software, functional safety and system design. With a portfolio and application knowledge covering the entire system, Danfoss has a unique ability to support OEMs in electrifying their applications.

Antti Väyrynen off-highway director. Danfoss’ Editron

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