Monthly Archives: July 2017

Raspberry Pi Zero Goes Wireless

The Raspberry Pi product line has added a new member, the Raspberry Pi Zero W (RBPiZW), an updated version of the RBPi Zero, with the added advantages on on-board Wi-Fi and Bluetooth capability.

Although the new RBPiZW lacks the Ethernet and full-sized USB-A ports, it is only a fraction of the size of its flagship brethren the RBPi, and less expensive as well. Almost identical to the RBPi Zero, the RBPiZW is twice as expensive, and boasts of a wireless chip supporting the 802.11 b/g/n Wi-Fi for 2.4 GHz only, and Bluetooth 4.0.

Both the RBPiZW and RBPi Zero use the same BCM2835 that powered the original RBPi. However, the single-core chip is now clocked at a higher speed of 1 GHz, as against 700 MHz earlier. On the RBPiZW is a Cypress wireless chip, the same the RBPI3 also uses. Although the Raspberry Pi Foundation has claimed the maximum wireless speed of the chip as 150 Mbps, in reality it generally hits about 20 to 40 Mbps.

Apart from the addition of the Bluetooth and Wi-Fi, there has been no change from the RBPi Zero to the RBPiZW. The designers added the Bluetooth and wireless LAN chipsets to the board, and included a PCB antenna layout licensed from ProAnt, Sweden.

The RBPiZW contains 512 MB RAM, a HAT-compatible 40-pin header, a CSI camera connector, a Micro-USB for power, Mini-HDMI port, a USB port for OTG, and headers for composite video and reset.

Although the new RBPiZW is a trifle heavier than its predecessor the RBPi Zero is, their dimensions are identical at 2.6×1.2×0.2 inches. You can also get a new case with the RBPiZW, with three interchangeable lids. The first lid is solid, the second has an opening in it for the GPIO pins, and the third has an opening for the camera module.

As the RBPiZW (and the RBPi Zero) come without the GPIO pins installed, they are able to maintain their slim profile, despite their full-sized GPIO headers. The user can solder the GPIO pins if the project demands, but the small size of the Zero boards are an advantage when using them to build a small robot or any other small system.

Even though the price is slightly higher, the RBPiZW remains incredibly cheap and is far more useful out of the box. Measurements of the performance of the tiny SBC confirm this. However, considering general performance when comparing with the RBPi3, such as during web browsing, it may be a frustrating experience. The RBPiWZ will have long pauses as the data loads and graphics renders in the Epiphany browser.

That means the RBPiZW is geared more towards hardware and software hackers, rather than those trying for a desktop experience. Those who want a replacement for their desktop computers would do well to use the RBPi3 instead.

Another factor weighing in for the RBPiZW is its low power consumption. Considering this board is meant for small systems and tiny robots, its low power consumption is a very big advantage when powering projects with batteries. Of course, the Wi-Fi support and network performance will affect its power consumption pattern.

SALTO the Agile Jumping Robot

In the Biomimetic Millisystems Lab at UC Berkeley, Duncan Haldane is responsible for numerous bite-sized bio-inspired robots—robots with hairs, robots with tails, robots with wings, and running robots. Haldane and the other members of the lab look at the most talented and capable animals for inspiration for their robotic designs.

The African Galago or Bushbaby is one such animal. It is a fluffy, cute, talented, and capable little jumping animal weighing only a few kilos. However, this little creature can jump over and clear bushes nearly two meters tall in a single bound. Biologists have discovered that Galagos’ legs are specially structured to amplify the power of their tendons and muscles. Haldane and his team accordingly made Salto, a legged robot weighing only a hundred grams, endowing it with agility and the most impressive jumping skills. Salto features in a paper the new journal Science Robotics.

Jumping is not only about how high one can jump, how frequently you can jump also matters. Haldane and his team have coined the term agility to refer to how far upwards one can go while jumping repeatedly. Technically, they define it as the maximum average vertical velocity achieved while performing repeated jumps. For a Galago, it can jump 1.7 m in height repeatedly every 0.78 s—an agility of 2.2 m/s.

Therefore, to be called agile, the jumper not only has to jump high, he also has to be able to jump frequently. For instance, although EPFL’s Jumper can jump to impressive heights of 1.3 m, it can only do so every four seconds. That means its agility is a measly 0.325 m/s. On the other hand, Minitaur can jump up only to 0.48 m, but it does so every 0.43 s, which gives it a much better agility of 1.1 m/s, despite its lower jumping ability.

That means improving agility involves jumping either higher, or more frequently, or both. Galagos are agile, because of not only their ability to jump high, but also their ability to do so repeatedly. Most jumping robots have low agility, because, they need to spend time winding a spring for storing up enough energy to jump again, and this reduces their jump frequency. The researchers at Berkeley wanted a robot with an agility matching that of the Galagos. With Salto, they have come close, as Salto can jump 1 m every 0.58 seconds, earning an agility of 1.7 m/s.

Just as with many jumping robots, Salto also uses an elastic element, such as a spring, for the starting point. For Salto, the spring, actually a piece of twistable rubber is placed in series between a motor and the environment, making a Series Elastic Actuator (SEA). Apart from protecting the motor, SEAs also allow for force control and power modulation, while allowing the robot to recover some energy passively.

Such springs are available to the Galagos in the form of their tendons and muscles. However, the leg of the Galagos is in such a form that allows it to output nearly 15 times more force than its muscles can by themselves. Haldane has used this same design for Salto as well.