Analysis of 6 design points of robot power architecture

To achieve innovation and stand out from the competition

The mobility industry is growing rapidly. By 2023 [World Robotics 2020], the market is expected to be worth nearly $30 billion, and in the near future, robots will be built to solve a variety of market problems by solving well-known and yet-to-be-discovered problems. They perform tasks that go beyond just moving from point A to point B: they make real-time decisions based on input data from the environment as well as their own tasks.

Power supply network with high power density and scalability

Figure 1: The M-Series operates from 43 to 154V input voltage to meet these needs. The DCM3623 enables regulated 24 or 48V power distribution from batteries to servos, other payloads, and downstream converters. The DCM3623 delivers 240W of power at 90% efficiency in a 36 x 23 x 7.3mm package. ZVS buck regulators or buck-boost regulators build the 24 to 48V line and can often be used to power lower voltage lines.

Providing these capabilities requires , and processing subsystems, but to stay ahead of the competition, robotic platforms must be able to quickly upgrade these components when better options become available. To achieve this quickly while maintaining size, weight, and cost targets requires a scalable and optimized power delivery network (PDN) that can meet changing needs. Considering the following questions will help you find the best answers for your platform. In this way, you can design a better PDN for your mobile robot that can withstand any changes caused by changing mission parameters.

01

Is your battery targeted for lightweight

Optimized for low-loss power distribution?

You worry about the economics (cost, power, lifespan) and lifespan (number of recharges, aging) of batteries, but have you considered whether the voltage you use will affect the overall weight of your design?

It's pretty simple, according to Ohm's law, you can reduce cable weight by distributing power at high voltage and low voltage, which requires thinner (lighter!) cables. Thinner, lighter cables are also smaller than larger cables, which reduces waste heat in the system. For these reasons, there are many battery power architectures based on 48V (and even higher!) compared to low voltage 12V solutions, and there are also high efficiency lightweight converters to choose from: including fixed ratio BCM and regulated DCM converters.

02

Has PDN been conducted for charging intervals?

Optimized to support current and future payloads?

Your platform will continue to evolve: faster speeds, more motors/actuators, and sensor arrays that need to deliver more functionality. Do you want to redesign your PDN every time you replace a subsystem?

Instead of redesigning your PDN, you can increase the overall battery capacity to store more energy using additional parallel cells at the same PDN supply voltage. Now you don’t need to redesign with a different voltage and deal with the ripple effects of associated changes across the platform. To optimize your future PDN, choose a high battery distribution voltage of at least 48V, and provide a discharge feature that allows the use of fixed ratio converters when needed to power subsystems. Fixed ratio converters are more efficient, smaller size, and lighter weight converters for step-down conversion. For example, your PDN can place these small modular converters anywhere you need to convert 48 to 12V or 800V to SELV voltages.

03

Whether dynamic load is given to the system

Adding unnecessary weight?

为动态负载供电的一种蛮力方法是调整 PDN 配电大小以获得更大功率，但如果负载具有低占空比，则需要一根大线缆显著增加重量才能满足需求。替代大型线缆的另一种方法是在负载点附近增加本地储能，在附近布置一款可在需要时供电的。然而，优化 PDN 可能还有更好的选项：固定比率转换器。这些转换器不仅可以像一款理想的变压器一样发挥作用，而且还具有从输入到输出（也支持从输出到输入）的反射的优势。这就意味着输入端的电容看起来就像输出端的电容，其扩展比率与转换器的转换 K 因数相同。更轻的解决方案将在固定比率转换器的输入端使用一个很小的电容值，而不是在一款转换器后面部署一款更大的电容器。

04

Should you develop a self-control plan?

Automating tasks is critical to improving efficiency, so even if your robot is currently controlled by a human, it is likely that some of these human-controlled tasks will be automated in the future. Looking at your current / you can see that the power requirements may be daunting, but the solutions already meet them. Planning for some additional power capabilities now (remember question 2!) will help you scale easily when you are ready to incorporate your enhancements.

05

Battery or cable?

Don’t underestimate the benefits of tethered designs, especially in situations where the workspace is limited, such as factories, warehouses, or arenas. Robots (including autonomous driving) are already using tethered power systems, which can transmit kilowatts of power through a small diameter cable. As shown in the figure below, the higher the voltage, the greater the power, given the same cable size (and weight).

Figure 4: The tethered cable supports indefinite operation time, so you can increase the voltage (to 400V, 800V, or higher) to provide more power as needed to support a wider range of functions on the platform (sensors, data collection, etc.). While this keeps the cable light, don't forget that lightweight converters can still bring you more benefits (remember questions 1 and 3?)

Some mobile robots require a tethered cable connection to a base station. In applications such as underwater inspection, tethers help extend the range of operations, allowing high-bandwidth data transfer from cameras in otherwise noisy and harsh environments. Thinner, lighter cables will allow these robots to operate at greater depths and distances, but thinner cables limit power delivery over traditional PDNs. Vicor's modular approach enables higher voltages to be transmitted over the cable, reducing cable size and weight without sacrificing power. Additionally, the small size and lightweight nature of Vicor modules reduces robot weight, increasing payload.

06

Is your modularization adding value?

Universal modularity is achieved by standardizing the mechanisms, data interfaces, and power supplies. Providing modularity at the FRU level of the system improves field maintainability. But there may be a time when your interface may lag behind the needs of your system application. For example, 12V has been the standard distribution voltage for computer and automotive PDNs for decades, but now 48V has become popular as power levels increase. To extend the value of modularity, you can use converters that can achieve efficient conversion in the PDN while maintaining the interface. Going back to the 48V to 12V example, the NBM2317 is a good example that can bridge 12V and 48V power supplies with a bidirectional and efficient conversion bridge.

Figure 6: The first power chain architecture highlights the high-performance buck-boost regulator PRM. The PRM can create a 24V to 48V intermediate bus with 96% to 98% efficiency to power the servo system and other downstream power modules, including fixed ratio NBM, ZVS buck regulator and ZVS buck-boost regulator. In addition, all modules can be connected in parallel to achieve higher power conversion.

A better way to power your business

These 6 questions will point you on the path to designing your PDN

◆ Perform power distribution with less heat and quality impact

◆ Disperse heat and promote heat dissipation

◆ Allows for increased battery capacity, eliminating PDN dependence on battery voltage

◆ Provide PDN scalability (power, capacity and autonomous control)

◆ Use common interfaces to achieve modularity to allow for future expansion of capacity

Editor: Huang Fei