WiBotic Gets Creative With New Wireless Charging for Robots and Drones
Different types of robots require different types of charging. Wibotic can keep options flexible by providing programmable onboard chargers.
WiBotic, a Seattle company that specializes in charging and power optimization solutions for robots, today introduced several new chargers and transmitters for drones and autonomous mobile robots. Let’s get more familiar with different aspects of this technology.
Wired or Wireless Charging?
You can find examples of autonomous wired chargers for robots and drones from different research groups. Since these systems rely on physical contact between the robot and the charging station, they are generally complicated systems. This is due to the fact that, with a wired solution, the robot position should be controlled precisely to connect to the charging station. This complicates the design and implementation and increases the cost of manufacturing.
On the other hand, wireless chargers are simpler, have lower maintenance costs, and reduce the chances of having a failed charging cycle. With wireless charging, we can seal the robots and make them robust to dirt, dust, water, or corrosion. That’s why a wireless solution can reliably operate, even in the most difficult applications and environments.
Besides, since wireless charging eliminates cables and connectors from the system, we can more easily create an interoperable solution.
Wireless charging of a UAV (unmanned aerial vehicles). Image used courtesy of A. B. Junaid
WiBotic’s Wireless Power Transfer System
The main elements of WiBotic’s solutions are shown below.
WiBotic's wireless charging system. Image used courtesy of WiBotic
The transmitter generates a high-frequency power signal that is converted to both electrical and magnetic fields by the transmitter antenna. The antenna can be mounted vertically in a wall station or horizontally in the landing pad of a drone. The onboard charger receives the energy emitted by the transmitter antenna and converts it to a DC voltage.
The onboard chargers are fully programmable. They can generate optimized charge cycles for a wide variety of battery chemistries. Batteries from 8-58.4 V and current levels from 0–30 A are supported. The programmable charger can produce the voltage and current levels suitable for the battery employed to maximize its lifespan.
Another important element of the system is control panel software that monitors the live charging process. Through the software, different charging parameters such as voltage and current can be adjusted for each robot depending on the application requirements.
Adaptive Antenna Tuning
There are two common wireless charging technologies: inductive charging and resonant charging.
In inductive charging, the relatively low-frequency power signal is transferred through closely coupled transmitter and receiver coils. That’s why the transmitter and receiver should be carefully aligned in inductive wireless chargers.
Resonant wireless chargers transfer a high-frequency power signal through coils that have the same resonant frequency. This enables energy transfer over several centimeters even when the coils are not tightly coupled. Resonant charging requires high-Q systems and is more complex than inductive charging.
The efficiency of these two methods versus distance is shown in the following figure.
WiBotic uses both inductive and resonant charging technology. Image used courtesy of WiBotic
As you can see, inductive charging is efficient at short distances. This method is not suitable for charging autonomous mobile robots and UAVs (unmanned aerial vehicles) because it relies on precisely controlling the robot position to ensure a reliable and efficient charge cycle.
Resonant charging technology has also a “sweet spot” where efficiency is maximized. Therefore, even with resonant charging, the robot should be able to navigate to the desired position accurately to ensure that the system can transfer power efficiently.
WiBotic claims that it uses a combination of inductive and resonant charging methods to enable efficient power transfer over a wider distance as shown in the above figure. According to WiBotic, the system monitors the connection between antennas in real-time and uses an adaptive antenna tuning process to maintain maximum efficiency even when the robot or drone cannot dock very accurately.
Now, let’s take a look at WiBotic’s latest products.
WiBotic’s New Onboard Chargers
Today, WiBotic announced two new onboard chargers: the OC-262 and the OC-150.
The OC-262 is a ruggedized 300 W charger that uses passive cooling. This onboard charger has no moving parts and is suited for harsh environments where water, dust, dirt, and corrosion are significant concerns. The product finds use in application areas such as the oil and gas, mining, construction, marine exploration, and agriculture industries.
Originally, the device was used for the Department of Defense. Now, however, the device is being unveiled to a wider audience.
The OC-262 is offered in two different models: an ST model with an IP20 rating and a WP model with an IP67 rating.
The OC-262 comes in an ST model and a WP model.
The OC-150 is a compact, lightweight charger designed for smaller robots and UAVs. It can provide up to 150 W. Depending on the battery type, the onboard charger can deliver up to 10 A with an output voltage ranging from 9 V to 58.5 V.
The OC-150 is a compact 150 W onboard charger.
WiBotic’s New Transmitters
The company also released two compact wireless power transmitters today: the TR-150 and TR-300 transmitters.
The TR-150 and the TR-300 can deliver up to 150 W and 300 W, respectively. These two transmitters are designed primarily for use with the OC-150 and the OC-262 onboard chargers. However, they are capable of pairing with other WiBotic onboard chargers when dealing with a system that uses different types of robots.
The GaN-driven power amplifiers of the new transmitters incorporate the latest high-efficiency GaN transistors from long-time partner GaN Systems to achieve an efficiency of 95 percent. The end-to-end wireless power transfer efficiency is reported to be 85 percent or more.
The TR-150 wireless power transmitter from WiBotic.
Why Do We Need an Autonomous Charging System?
There are several applications that employ a fleet of robots. For example, in military operations, a fleet of UAVs can improve situational awareness over areas of interest.
Another example is automated warehouses, which use a fleet of robots to transport materials. Increasing productivity by two to three times, warehouse robots are accurate and cost-effective.
Modern warehouses employ a fleet of robots to transport materials more efficiently. Image used courtesy of AJC
Depending on the size of the system, it can be very challenging to track the charging status of the drones or robots. As such, an autonomous charging system can increase battery intelligence for maximum uptime.
Looks like a highly useful idea. I am interested to find out which part of the RF spectrum you are going to use for the resonant type. I can see the advantage of it but on the other hand there is a cost, as every coil acts as an antenna and the amount of power being generated is by no means small. Depending on which frequency is being used, one or more services that use that frequency band are likely to suffer interference particularly as you will most likely not be using pure sine waves; switching transients spread RF garbage which at that power level will be quite significant.