New and innovative vehicles are being developed to support more autonomous activity in transport for warehousing, logistics, agriculture, and distribution. The power requirements for these applications have triggered the development of new solutions from semiconductor manufacturers.
Electrification in the automotive industry continues to generate headlines as consumers want to learn more about the features and benefits of electric passenger vehicles, predominantly cars. In the engineering community, the conversation often turns to power: the high voltages and large batteries used in electric vehicles, with power distribution networks that must handle 400 to 1200 V DC.
There are many examples of battery-powered solutions within the e-mobility category, from small single-person transportation to buses for mass transit. While there is definite momentum behind these examples, the benefits of electrification also extend to vehicles for transporting goods on roads, agricultural equipment, and warehousing for logistics and distribution.
Vehicles designed to move people quickly over long distances on open public roads come with demands for long-range (in other words, large batteries), high payloads (large motors), and safety restrictions (limited autonomy). In comparison, small electric vehicles designed for warehousing or smart agriculture move more slowly, carrying smaller payloads over shorter distances in controlled environments. As a result, this class of electric vehicles is pioneering higher levels of autonomy.
We can categorize electric mobility by the battery voltage. Vehicles for people tend to have larger and more complex battery requirements than vehicles used exclusively for moving objects, such as goods on pallets. The category focused on warehousing is experiencing high levels of innovation while also becoming more accessible to business owners. These robotic vehicles can be simpler to design, customize, optimize, and deploy. They can also have relatively lower operating costs, often providing a shorter time to payback with more evident results.
Electrification in wider transportation sector
The use of electrically powered devices in logistics, warehousing, and agriculture is already established. For example, pallet trucks and forklifts have been electrified for many years. However, autonomous mobile robots (AMRs) and automated guided vehicles (AGVs) are defining the way these devices evolve further.
While there are similarities in their form and system-level functions, the differences between conventional solutions, AGVs, and AMRs illustrate the diversity in electrification. Some of these differences are summarized in the table below:
The simple color coding in the table shows that AMRs offer the most benefits based on the highlighted features. Of course, there are other considerations, such as total cost of ownership and maintenance. However, the cost of an AMR or AGV is expected to be lower than that of a forklift, meaning the cost of ownership amortized over the working lifetime will also be lower.
Diversity in application brings with it diversity in requirements. Each type of vehicle will need systems optimized for its size, type of mobility, range, payload, and overall weight. As scale is reduced, smaller vehicles can operate with smaller electric motors requiring lower voltages and smaller batteries.
Autonomous versus guided
Autonomy underpins the productivity gains that can be made from using machinery. Even simple machines perform some functions autonomously. For machines designed to be mobile, autonomy takes on a different meaning, as they also need to navigate within their surroundings.
An autonomous vehicle navigates using sensors to understand its environment. It will also know where it is moving to and probably decide its route. Alternatively, a guided vehicle moves autonomously, but its navigation and destination are controlled off-board. This often means using markers or waypoints that tell the vehicle when to change direction or when it has arrived at its destination. In a conventional vehicle, the operator handles the navigation, although they may have some assistance, such as position detection and mapping.
The main difference between a conventional electric pallet truck or forklift and an autonomous or guided alternative is clear: the operator no longer needs to be physically present. This also means the vehicle’s design isn’t human-centric; it doesn’t need to provide space or capacity for a human operator. With no human operator present, the size and shape of the vehicle can be much more application-specific.
As a result, we can expect greater innovation in autonomous and guided vehicles brought to market. Creating a common platform for these products will accelerate the design cycle while allowing customization with respect to the function and payload. While navigation will depend on the vehicle category, the power and motion subsystems are functions OEMs could consider standardizing. The precedent for this has already been set by car OEMs, who now openly share common platforms for EV development, potentially spurring ongoing innovation.
AMR/AGV power subsystems mid-voltage solutions
Regulations cover the identification of voltages used in transportation applications. Low voltage covers systems up to 20 V DC and are color-coded using wires with black insulation. Anything between 20 V and 60 V is classified as mid-voltage and color-coded with light blue wiring, housings, and conduits. Above 60 V is classified as high voltage and is color-coded using orange cables, housings, and conduits.
Most EVs and all BEVs will have orange wiring, denoting the high voltages they use. Many may also have light blue wiring, where 48 V systems are used. Mild hybrids may only have 48 V electrical systems.
The use of 48 V is becoming more common across various subcategories of electric mobility. It falls within the mid-voltage range, so technically, these systems are not restricted to only operating at 48 V; they could operate at up to 60 V DC. This makes mid-voltage a flexible choice for smaller autonomous electric vehicles.
In some cases, specifically within mainstream automotive, 48 V is also used instead of legacy 12 V systems. Moving from 12 V to 48 V means a lower current for the same power. Carrying lower current means lower losses over the same distance through the same wiring harness. Moving to 48 V to deliver the same power in new applications means a lower gauge wire can be used in the harness.
As the voltage increases, the cost and weight of the wire used in the harness decrease. Interconnections can use smaller or more densely packaged terminals, which positively impacts the size, cost, and weight of connectors. These are obvious advantages when designing power architectures for small autonomous or guided vehicles.
Mid-voltage power architectures’ electronic components
In addition to the wiring and connectors needed, these power architectures are based on electronic components. These components fall into a hierarchy, including:
- Discrete components: transistors, diodes, and transient voltage suppressors
- Integrated solutions: High-side and low-side switches
- Modules: AC/DC and DC/DC converters
These components are typically individually selected and designed into systems based on specific requirements.
The semiconductor industry has been designing and manufacturing these products for decades. However, the industry reacts to market demand. Historically, demand from the automotive and industrial verticals has not been strong for mid-voltages, but that is changing.
Indeed, although the shift toward mid-voltage for automotive and transportation applications is relatively recent, the industry is actively responding to the growing demand for this class of semiconductor components.
To meet this demand, semiconductor manufacturers are developing solutions designed for the 20 V to 60 V range. This results in devices optimized for switching or otherwise controlling voltages up to around 100 V DC. Those same types of components already available for other power applications are typically designed and optimized for voltages either below or above 100 V.
Although developing these solutions has undoubtedly presented some technical challenges, manufacturers are experts in this field. Part of the challenge is developing devices optimized for the market in terms of cost and performance. As the market evolves, we can expect to see more solutions coming to market.
Many of the industry’s leading power semiconductor suppliers already have products designed for mid-voltage automotive and transportation applications available today. Most have announced roadmaps for more products targeting mid-voltage applications.
The increasing demand for mid-voltage solutions indicates the direction of the automotive and industrial sectors. We can expect increased availability of e-mobility solutions for both passenger vehicles and solutions designed for other types of transportation.
About the author
Jason Skoczen is currently the Avnet Sales Director of Lightspeed and Transportation with more than 16 years with the company. Jason started at Avnet as an intern in 2007 in Phoenix. After graduating from Michigan State in 2008, he was hired as an Account Manager with the Avnet Heat program and relocated to Irvine, California. After a nine-month stint in Irvine, Jason moved to Phoenix to help develop the newly formed centralized Tier 1 EMS team as an ISR. After two and a half years in that role, he then moved to Milwaukee to become an Account Manager. Over the next four years, he began calling on automotive customers and became the Supplier Business Manager, driving Avnet’s newly developed automotive strategy. Five years ago, Jason was promoted to his current role, where he continues to lead Avnet’s automotive sales development.
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