According to the International Federation of Robotics (IFR) (www.ifr.org) there were almost 2.5 million industrial robots deployed in 2018 and this number is growing at more than 400,000 units annually. The industrial, automotive and electrical/electronic sectors represent over half of total deployments with metal and machinery, plastics and chemical and food and beverage being significant users as well. Approximately 75% of all industrial robots are deployed in China, Japan, USA, Korea and Germany.
The rapid adoption of robots is not confined to the industrial sector with 250,000 ‘professional service’ robots deployed by 2018. This represents a staggering growth of more than 60% on the prior year. Two-out-of-five deployed service robots are classified as autonomous guided vehicles (AGVs) used primarily in logistics and manufacturing. The personal and domestic robot market grew similarly (c60%) and now comprises around 16.3 million units used for a variety of tasks ranging from vacuuming to education and research.
48V & Robotics
48V has become popular in a number of applications due, at least in part, to the fact that it is the highest safe voltage in common use. This allows designers to reduce the system protections compared with mains powered devices and also reduce the size of conductors (compared to 12V-powered products), thereby reducing weight, cost and power losses. Motors that are powered directly by 48V are also generally smaller and, in robotic applications, this allows for smaller and lighter joints, thereby increasing machine efficiency, dexterity and reliability while reducing weight and cost. In turn, this opens-up more potential opportunities for robot use to improve automation of processes in all industries.
48V is very popular in many modern applications including automotive where it is rapidly becoming preferred over 12V for many onboard devices, and cloud computing where 48V power distribution is used for server backplanes, cooling fans and other telecom-related applications. This prevalence means that devices and sub-systems for 48V power are commonly available, increasing choice for designers and lowering costs through economies of scale.
Figure 1: High-level block diagram (including power system) of a typical robot
Robots are fairly complex systems and, depending upon the application and functionality, will comprise a number of functional elements including connectivity, image sensing, position sensing, and motor control. There are also a number of different power sub-systems including AC/DC conversion, battery management, DC/DC conversion, multiphase converters, point-of-load (PoL) conversion, linear regulation, and motor drivers. Each of these areas requires an efficient solution for the robot to operate as the designer intended.
If we were to look at similar functional block diagrams for automotive or cloud computing systems, we would find a significant number of similarities with the robot block diagram. This brings opportunities to cross-pollinate power solutions from other applications to robotics. As an example, eFuses are used extensively in cloud computing to allow for hot-swapping of storage media and cooling devices such as fans. However, in a robotic application, the same eFuses could be used to introduce modularity, thereby permitting functional blocks (such as tool pieces) to be exchanged by the robot itself – even in the middle of an operation, depending upon the task in hand.
Delivering power solutions for 48V robotic applications
Many modern robotic applications utilize a 48V bus to transport power around the system. Compared with a typical 12V bus, this offers 1/16 of the losses or allows thinner and lighter cables to be used. In fixed robot installations, the 48V will be generated by a mains-fed power supply that will incorporate a power factor corrected (PFC) front end. Mobile robots, such as drones, care assistants and others will have an on-board battery that is replenished periodically from a mains-powered adapter.
Few semiconductors are able to work directly from 48V, generally requiring voltages of 5V down to the sub-volt level. The non-isolated PoL converter plays an important role here converting a higher voltage to the level required by the IC. In some cases, an intermediate bus voltage (typically 12V) would be created by using an intermediate bus converter (IBC) that is loosely regulated with the PoL converter converting the 12V to the supply voltage for the IC. Increasingly, single-stage conversion is preferred and many PoL converters are now available to convert directly from the 48V rail to the IC supply voltage.
As with every power solution, the power architecture for a robotic application is required to be efficient and reliable, as well as offering high levels of power density so that the robot can be small and nimble enough to perform its function(s) well. Key to achieving this is to select the right semiconductors to form the various power functions within the robot.
Semiconductor solutions for robotic power applications
ON Semiconductor is an example of a company that has applied expertise and invested to offer a wide range of devices and power products that offer designers the ability to design high-performance power solutions for robotic applications.
One of the most common devices used in almost all power solutions is the MOSFET. ON Semiconductor’s extensive range includes ‘super junction’ MOSFETs with multiple versions for different switching types and applications. The FAST devices offer high efficiency in hard switching topologies, while the easy drive devices are suitable for both hard and soft switching applications where they ensure low EMI and reduced voltage spikes.
Complementing the MOSFET offering are a wide range of high voltage gate drivers that allow a microcontroller or other logic circuit to control MOSFETs directly. Depending upon the circuit configuration, a simple non-isolated driver (such as ON Semiconductor’s NCD570x series) may be used, or a more sophisticated isolated solution or a high and low side driver may be needed.
Highly integrated solutions such as intelligent power modules (IPMs) and automotive power modules (APMs) bring a number of benefits. Typically, these will integrate multiple MOSFETs for multi-phase motor driving along with the necessary driver devices. Compared to discrete solutions these modules offer better thermal performance as all devices are mounted on the same substrate. They are also able to handle higher current levels while improving EMI and providing a solution that is smaller and lighter than a discrete solution.
Alongside these solutions, ON Semiconductor offers a complete portfolio for robotic power applications including eFuses, PFC ICs, rectifiers, current sensors and switching devices for providing auxiliary power rails. This is complemented by the industry’s lowest power Bluetooth module for communication and a wide range of image sensors for advanced machine vision.
By Ali Husain, Corporate Marketing & Strategy, ON Semiconductor
>> This article was originally published on our sister site, Power Electronics News.