Advanced servomotors and software are making entertainment robots smarter and more capable than ever before.
Imagine you're at a trade show and this robot singles you out for a conversation. Sure, it's just a robot, but how does it know your name? And there's something hauntingly human about the assembly of sensors, cylinders, and mechanical links. The answer lies at the end of an umbilical in a large trailer outside. There, amid a whirring collection of computers, hardware, and monitors, is the brain behind the bot: A human operator wearing a sensor-laden suit serves up the banter and body language while Max the anthropomorphic robot mirrors it all in real time. Video cameras in Max's eye sockets feed to a virtual-reality headset, affording the operator a view of the show — even your nametag.
While all this may seem recent, Max is pushing six years old, an eternity in terms of electronics technology. The basic mechanical design is still viable and Max continues to do trade shows worldwide. But improved servomotors, computers, and software will make Max's successors — an Illano-type robot (original Illano predates Max) and Sico-8 — easier to build and operate. Sico-8 is under construction and will be driven directly by servomotors. The new Illano-type robot, in contrast, shares Max's Aquadraulics motion system.
Aquadraulics is a novel, lowpressure, water-based hydraulic system developed by the robot builder Mannetron Inc., Battle Creek, Mich. It was an Aquadraulic system that ran the moon-faced piano player robot for restaurant-chain McDonald's popular Mac Tonight publicity campaign about nine years ago.
The Aquadraulic system for Max and the brothers Illano drives 34 movable axes, each fitted with either a double-acting cylinder or a rotary actuator. Each axis pipes back to a separate double-acting cylinder located in the robot platform or stage. Servomotors coupled to linear actuators precisely move the platform-mounted cylinders which, in turn, move the related joints. "Basically, the platform-mounted assemblies act as master cylinders and the limbmounted hydraulic units as brake calipers," explains Mannetron CEO Mike Clark. A pump maintains system pressure at about 250 psi, much lower than conventional hydraulic systems. This makes the system more reliable and simpler to maintain. And because it circulates a mixture of water and RV antifreeze, leaks are easier to mop up. Though Max and the new Illano-type robot are mechanically similar, electronically they are miles apart.
Wires, wires go away
Consider Max's control system. Raw data from the operator-suitmounted sensors go to a Windows computer then to a prescaler. From the prescaler, it pipes to a DOS-based computer. The DOS computer does some calculations and directs the updated information to a bank of DSP cards. The DSPs input to servoamps that power the servomotors. Feedback from motor-shaft-mounted encoders (commanded) compare to data from position sensors on robot extremities (actual). The difference between the commanded and actual positions or error signal corrects the DSP input. The system then gets the next command from the suit-borne sensors and the process repeats — 30 times/sec. This speed matches standard video rates of 30 frames/sec so robot movements appear smooth to human observers. Further helping to tweak response is a special gain control box. The box uses analog-style knobs to control digital PID gains. "The knobs are much easier to use and more intuitive than plugging in numbers, especially for coordinated motion on multiple axes," says Clark.
Precise gain control helps eliminate jerky motion as does the video-speed updates. But high bandwidth also places unusually high demands on servomotor response. So-called pancake servomotors use a printed-circuit rotor to lower rotational inertia. The lightweight rotor lets the motor rapidly change speed and direction but also makes it susceptible to damage from overheating. Because the motors are stand-alone units, wiring tends to be complex. The motor encoders mount externally, and the DSP cards and servoamps both reside in separate locations in the robot stage.
Contrast this with the new Illano-type robot-control system. It will hook the operator sensor suit directly to a dedicated Windows PC. The PC runs a real-time Windows driver dubbed Syncon specially developed for the application by Mannetron. Though details are proprietary, "Syncon taps into microprocessor hardware in such a way that eliminates dropped frames and the resulting twitchy motion," explains Peter Jungen, a computer software engineer at the company. "We designed Syncon for robots but it could also control machinery and processes."
Output from the Syncon driver pipes directly to new SmartMotors from Animatics Corp., Santa Clara, Calif. These brushless servomotors contain a controller DSP, servoamp, and a 2,000 count/rev shaft encoder, all within the motor housing. The built-in DSP handles all the lowlevel, real-time calculations, freeing the CPU to more smoothly coordinate robot motion, says Jungen. Encoder data goes to one port and power and RS-232 compatible signals to another. Such brushless servomotors electronically commutate a wound stator to drive a permanent-magnet rotor. Mannetron found the arrangement better transfers heat to the motor housing for cooler running, an important consideration for the application. Moreover, the integrated motor controls eliminate the racks of hardware and literally miles of wire.
Speaking of wires, the Illanotype robot does away with the umbilical and instead connects with its remote human operator by wireless link. A proposed 900-MHz spread-spectrum transmission scheme sports a two-mile range and should have the required bandwidth for real-time operation. A small dish transceiver, similar to those on some delivery trucks, relays the signals to and from the robot site.
The wireless link will make the operator station more mobile, but Max's successor is still bound to a stage and the Aquadraulics system contained therein. Such robots aren't designed to move about. However, the soon-to-be completed Sico-8 is.
On a roll
Rather than an Aquadraulics system, Sico-8's 10 axes are to be fitted with SmartMotors. The drive rollers, elbows, wrists, head, and torso all will be motor driven and controllable through a pocketsized device via a similar but enhanced spread-spectrum method. Pushbuttons on the controller link to each axis. Several buttons pressed simultaneously could issue the macro command "reach," for instance. Unlike earlier line-ofsight robots that require the operator to be in the immediate vicinity, Sico-8's operator can be in another part of the building. They will view images from the robot's eye-socket cameras on virtual reality glasses and talk with showgoers over a two-way radio link. When the human operator needs a break, Sico-8 can do a canned shtick stored in memory. As they say in show biz, the show must go on.
"Entertainment robots are great fun and will continue to grow in popularity. Eventually, though, I'd like to see smart robots do maintenance in space, clean up hazardous waste sites, even diffuse bombs. Can you imagine telling a robot to ‘Go get the bomb', and it does? It'll happen. The technology already exists." — Mike Clark, CEO Mannetron Inc.