Why and how to use a component-based distributed power architecture for robotics
management and order fulfillment tasks within large warehouse environments. This robot class is typically powered from a 24 to 72 volt battery source with opportunity charging performed on an as-needed basis Component-based distributed power architectures for robotics This section reviews four examples of component-based distributed power architectures for robots ranging from a 15.9 kilowatt (kW) system for agricultural harvesting robots with a 760 volt battery pack down to a 1.2kW system for warehouse inventory movement robots using a 48 volt battery pack. A common feature in three of these
Figure 3: The PDN for warehouse robots combines a 67 volt main power bus and a 48 volt intermediate power distribution bus. Image source: Vicor
system efficiency and reduces power system weight and cost.
Distributed power architecture design considerations
As shown above, designers must make numerous power system choices to optimize a component- based PDN for robotics. There is no ‘one size fits all’ approach. In general, larger robots benefit from higher battery voltages which can result in higher power distribution efficiencies and smaller, lighter power distribution buses. The use of isolated versus non- isolated DC/DC converters is an important consideration when optimizing overall system efficiency and minimizing costs. The closer the DC-DC converter is to a low- voltage load the more likely it is that the optimal choice will be a lower cost, non-isolated power component, increasing overall PDN efficiency. When appropriate, the use of lower cost fixed-ratio (unregulated) DC/DC converters
Figure 4: The PDN for warehouse robots using a 48 volt battery pack eliminates the need for an intermediate power bus, greatly simplifying the design. Image source: Vicor
step-down sections that deliver the needed power to the subsystems. A high-voltage power distribution bus results in improved efficiency and lower power distribution currents which allows the use of smaller, lighter and less expensive power cables. The fourth application shows the simplification that can result in smaller robots that use 48 volt battery systems.
comprises a 760 volt main power bus (Figure 1). This is supported by a series of fixed ratio (unregulated) isolated DC-DC converters (shown as BCM modules on left) with an output voltage of 1/16 of the input voltage. These converters are used in parallel, enabling the system to be resized according to the needs of the specific design. Further into the network, a series of fixed ratio (NBM, upper middle) and regulated buck-boost (PRMs, center) and buck converters (bottom) power downstream, lower voltage rails as needed. In this design, the servo is driven directly from the 48 volt intermediate power bus with no additional DC-DC conversion. The PDN for campus and consumer delivery robots shows the simplification that can result in medium power systems by employing a lower main power bus voltage (in this case, 100 volts), and adding regulation to the isolated DC-DC converters (DCMs) on the
main power distribution bus to produce the 48 volt intermediate bus voltage (Figure 2). This approach enables the use of non-isolated buck-boost and buck DC/DC converters to power the various subsystems. In addition, the use of a lower voltage for the main power bus enables the motor drive to connect directly to the main bus, while the servo can connect directly to the 48 volt intermediate bus. Smaller campus and consumer delivery robots may incorporate a 24 volt intermediate bus voltage and either 24 or 48 volt servos, but the overall architecture is similar. The PDN for warehouse robots using a 67 volt battery pack highlights the use of buck-boost
non-isolated DC-DC converters (PRMs) on the main power bus (Figure 3). These converters provide efficiencies of 96% to 98% and can be paralleled for higher power needs. This architecture also features a fixed ratio, non-isolated DC/DC converter (NBM) to power the GPU, and non-isolated regulated buck converters powering the logic sections. For smaller robot designs using a 48 volt battery there is no need to generate an intermediate bus voltage, simplifying the design (Figure 4). The loads are powered directly from the battery voltage by direct conversion using various non-isolated DC/DC converters. The elimination of the intermediate bus in the power train increases
applications is a relatively high voltage main bus that distributes power throughout the robot, followed by one or more voltage Figure 2: The PDN for campus and consumer delivery robots includes direct drive for the motor and an intermediate bus to power the remaining subsystems. Image source: Vicor The power delivery network (PDN) for agricultural harvesting robots
A high-voltage power distribution bus results in improved efficiency and lower power distribution currents which allows use of smaller, lighter and cheaper power cables.
Figure 5: The DCM3623TA5N53B4T70 isolated and regulated DC/DC converter can produce the 48 volt intermediate bus voltage from 100 volt battery power. Image source: Vicor
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