E-Mobility Engineering 017 l ECE Doosan electric excavators dossier l In Conversation: Matt Faulks l Battery testing focus l Battery Show North America 2022 report l Ariel Hipercar digest l Cathode materials insight l Thermal management focus

movement is the Doosan EPOS, which holds the intermediary algorithms between the hydraulics controllers and the e-motor. “It’s through that original Doosan EPOS that the operator is also able to control key safety-critical functions such as braking and steering, and it also manages the display screen,” Van Hal says. “The EPOS connects via an SAE-J1939 standard CAN 2.0 bus to the Rexroth controllers managing the lifting and traction drivetrains. Based on what the Rexroth systems communicate, the EPOS sends rpm requests to the powertrain ECU, and the ECU communicates with our main controller for the electric conversion- related systems, overseeing the power distribution, the onboard charger’s controller, the BMS, and our low- voltage subsystem controllers for the cabin and the HVAC.” The main controller is a Danfoss Plus+1 MC050 machine management system, designed principally to function as part of a distributed network of intelligent control nodes such as that in the electrified Doosan excavators. The M050 is powered by a 32-bit ARM Cortex-M3 processor, which has 512 kbytes of flash memory and features a nested vectored interrupt controller (NVIC) for processing up to 240 interrupt signals with low latency. The NVIC can also be used for assigning priority levels to signals within the bus coming from different sections of the electric powertrain based on user configurations, with the possibility for dynamic reprioritisation, which might be critical during hazardous scenarios such as motor failures or battery packs running excessively hot or cold. Also, as can be inferred from the name, the MC050 comes with Danfoss’ Plus+1 guide software, which is designed as an assistive graphical tool for machine application software development, without its end-user needing to be experienced in programming. It is designed to allow modular dragging and dropping of function blocks into algorithmic flow diagrams, enabling rapid addition or exchange of modules for managing sensors, valves, pumps and motors, as well as allowing for PID control, ramp rates and filters, all the while generating source code directly from the end- of ZF axles: a rear axle upon which the hydraulic transmission mounts for optimal protection and ground clearance, and a front axle designed to achieve wide oscillating and steering. And as on the DX300LC, this pump also drives an axial piston motor with a two-stage planetary gearbox, at up to 14.6 rpm with 3608 kgf/m. Braking is achieved through disc plates engineered for working on wheels rather than treads. Initial actuation of the brake and steering systems is performed by dedicated gear pumps, with valve-controlled auxiliary circuits connecting the hydraulic fluid to these systems. Despite the parasitic losses inherent in hydraulics, ECE plans to continue using them for the foreseeable future, not only for their greater practicality over electro-mechanics but also because replacing them would drive up the total cost of ownership. However, a lot of room for improvement is still possible through the control software, Van Hal notes. “For instance, the hydraulics controller by default still requests 900 rpm of the e-motor when idle, as that’s the speed the diesel engine idles at,” he explains. “Soon we’ll be testing a patch that changes this command to request just 100 rpm or maybe 0 rpm of the electric machine, because the pumps only ask for idle when they don’t need any power.” Computation and connectivity As discussed, the main vehicle computer executing the operator’s commands for excavation and Specifications DX165W Electric Weight: 17 t Bucket capacity: 0.64 m³ Maximum digging depth: 5.02 m Voltage: 800 V Battery capacity: 280 kWh Peak power: 158 kW Maximum speed: 40 kph Typical speed: 35 kph DX300LC Electric Weight: 34 t Bucket capacity: 1.27 m³ Maximum digging depth: 7.3 m Voltage: 800 V Battery capacity: 420 kWh Peak power: 251 kW Maximum speed: 5.5 kph Minimum speed: 3 kph A certified 800 V heater will be used in the near future for the excavators’ thermal management and HVAC systems (Courtesy of Webasto) The hydraulics throughout the arm, bucket, traction and rotation mechanisms have been mostly unchanged, as they are still more efficient than replacing them with current electro-mechanics 32 January/February 2023 | E-Mobility Engineering