Emerging Properties: Robotics - Simply Sensors & Servos

Team members have met several times since last blog posting .... high-level overviews of both spheres (Robotics & AI) were presented along with an introduction to MS Robotics Studio. This blog posting will focus on Trev's robotics overview.

Servos & Sensors pretty much covers the 2 major divisions of robotics hardware. Very simply, if you want the robot to move at any junction point (hip, elbow, knee, etc) - you need a servo. If you want the robot to sense its environment - you need a sensor.

SERVOS
Servos are primarily driven by the rotational movement of a motor. Servos can usually move bidirectionally (forward and backward) and only have 2 primary functions.... 1) Receive commands and 2) Send state information. These functions are usually implemented via attached microcontrollers. State information is derived by the motor's ability to sense its position and track its speed. Some servos report their speeds via the use of a tachometer which correlates a voltage proportionally to a rotational speed. Central to the role of servo control is the concept of negative feedback which is defined as a type of feedback in which the system responds in an opposite direction to the perturbation. A servo controller is a microchip that interfaces directly with the motor control. The motor and servo controller come to a desired result (command) through a two-way conversation described as "hungry or less hungry". Not the last time this "hunger" concept will surface during this meeting.

SENSORS

Sensors that we will primarily being dealing with can be grouped into 3 major camps ... Acoustic, Electromagnetic and Mechanical. Acoustic sensors detect pressure waves in air or water. Sonic and ultrasonic sensors can be used to detect sounds or physical objects (via echo-return sonar).

ACOUSTIC: Common acoustic-based sensors include microphones (for sound) and ultrasound sonar for object/obstacle detection. Positional data during obstacle detection using sonar may be limited to distance measurement only (without reliably providing the angle relative to sensor).

ELECTROMAGNETIC: Infrared sensors detect energy from the infrared portion of the EM spectrum (longer wavelength then visible light but shorter than radio waves). Infrared-based robot sensors can be used to detect heat differences in a field of vision and object/obstacle detection. Ultraviolet robot sensors provide limited obstacle detection & heat detection. Arguably the most important robotics-based sensors revolve around the visible light portion of the EM spectrum. Optical sensors are a primary tool in robotic sensory hardware .... your everyday webcam is a perfect example of an optical sensor (so are your eyes). Obviously, optical sensors are used for object detection in a field of vision and binocular optics (2 web cams) can help in providing the potential for excellent positional and relative angle information for objects in the field. This "richness" of data also has its darkside.... it provides reams of information that if processed/analyzed at any reasonable frame rate (1-50 frames a second) can bring any modern computer to its knees.

MECHANICAL: Bumpers are a good example of a mechanical sensor. These sensors can provide both a positional value and a force strength value when used for collision detection. The image to the left is a simple LEGO based bumper implemention using touch sensors by young kids at a primary school. Other interesting examples of mechanical sensors are human skin and animal whiskers. A substantial amount of literature on whisker-cortex signalling in the rat and cat exists and may serve as a useful model in small robot development. A robotic skin substrate that is tied to an array of mechanical sensors may serve as a powerful addition to any robot implementation.

Trev wrapped up the robotics overview by discussing that simplistic robot designs are usually just a collection of servos and sensors controlled by their respective microcontrollers leading to a master controller (sometimes called a Stamp) that manages the interplay amongst all the pieces by proprietary software (usually specific to controller chipset). Cabling was also mentioned as an important aspect of robotic design that can affect robotic performance.

TEAM GOALS:

ROBOT DESIGN: The team initially discussed rover-based designs for our initial set of robot prototypes but we then decided to focus on bipedal based robot designs in light of the fact that "black box" self balancing robotic bipedal leg platforms are already on the market. We may fall back to 4-leg designs if we "stumble" too often but I admire our ambition (even if foolhardy ... )

ROBOT BEHAVIOR GOAL: After having major discussions on robotic philosophy, robot feelings and robot love (don't ask).... Rob was getting ready to segue into his presentation on Artificial Intelligence and HTMs. We semi-concluded that our first major milestone should be to tie an HTM-based AI to a bipedal robot who's life mission is survival. Initial thoughts revolved around the concepts of hunger (there it goes again) and having the robot define its "hunger" as an inverse relationship to its reserve energy level (battery charge level).... while defining its "food" as light energy that can be fed into solar panels thus raising its charge level.

After laughing hysterically of the notion of our robot running head-on into the headlights of an oncoming vehicle or killing itself because it couldn't lift the shades at a window... we decided that a bipedal robot that can effectively move about seeking well lit areas ... may be a suitable initial goal.