COMP790-058 RoboticsSensorsSlide 3CamerasStereoscopic VisionStereo RangingMonoscopic VisionObject RecognitionActuatorsSlide 10Slide 11Slide 12LocomotionLegsWheelsExotic Wheels & TracksRecent TrendsMobility ConsiderationsSlide 19Slide 20ManipulationsManipulation Actuator TypesMeasuring Motion: OdometersMotion TypesIntroduction to KinematicsManipulator Joint TypesMore Joint TypesForward vs. Inverse KinematicsUNC Chapel HillD. ManochaCOMP790-058RoboticsSensors & ActuatorsIntroduction to KinematicsUNC Chapel HillD. ManochaSensorsVision (Review)–Stereoscopic–Monoscopic Sonar (see a later lecture)Others (bump sensors, LIDAR, etc.)UNC Chapel HillD. ManochaSensorsSensors are devices that are used to measure physical variables like temperature, pH, velocity, rotational rate, flow rate, pressure and many others. Today, most sensors do not indicate a reading on an analog scale (like a thermometer), but, rather, they produce a voltage or a digital signal that is indicative of the physical variable they measure. Those signals are often imported into computer programs, stored in files, plotted on computers and analyzed to death. http://newton.ex.ac.uk/teaching/CDHW/Sensors/http://www.facstaff.bucknell.edu/mastascu/elessonshtml/Sensors/SensorsIntro.htmUNC Chapel HillD. ManochaCamerasCharge coupled devices (CCD’s) use arrays of photosensitive diodes to generate intensity maps–grey-levels of color devices are available–a range of image resolutions (pixels per image)•800 × 600 pixels is typical–a range of frame rates (number of images per second)•30 Hz (frames per second) is typicalThe field of view can be changed–high-resolution cameras typically view 45 - 60°–wide-angle (fisheye) lenses may cover 80 - 90°–curved mirrors increase field further without distortionUNC Chapel HillD. ManochaStereoscopic VisionViewing the world with two cameras (eyes) allows a 3D representation to be formed–unfortunately the signal is complex and noisyEach camera receives a slightly different view–the distance between corresponding points in an image is known as the stereo disparitydisparityUNC Chapel HillD. ManochaStereo RangingThe amount of disparity is related to distance–the difficulty lies in identifying corresponding pointsThe general principle is–left and right images are digitized–raw images are rectified for distortion / misalignment–rectified images are filtered to enhance textures+edges–a stereo matching algorithm is applied•modern techniques search along horizontal scan lines to find the best set of matching pixels (e.g. mean-squared-error)–raw disparity map is filtered to remove noiseThis can now be done on modern computers–e.g. Pentium P-4 @ GHz at interactive frame ratesUNC Chapel HillD. ManochaMonoscopic VisionAlthough stereo vision is popular, it has problems–high hardware requirements, camera alignment, etc.–consequently single camera input may be used alsoMonoscopic ranging–optical flow•the relative motion between the moving camera and viewed objects in the environment, seen over a sequence of images–looming•as an object gets close, it gets bigger!•is simple to use this information to calculate distance–but the object must have been identified and must be totally in view–depth from focus•depth-of-field of conventional lens systems can be usedUNC Chapel HillD. ManochaObject RecognitionMuch vision research on object recognition –so easy for humans, but the problem not yet solved –humans may use a combination of techniques and reasoningEdge detection–fairly simple filter operations can detect clean edges•e.g. the discrete Laplace filter–reliable detection of all edges is much more difficultArea based techniques–connected regions of similar color, texture or brightness probably belong to the same objectUNC Chapel HillD. ManochaActuators An actuator is a mechanical device for moving or controlling a mechanism or system.Mechanics - plasma actuators, pneumatic actuators, electric actuators, motors, hydraulic cylinders, linear actuators, etc. Human - Muscles Biology - Actuator domains found in P, F and V type ATPasesUNC Chapel HillD. ManochaActuatorsIn engineering, actuators are frequently used as mechanisms to introduce motion, or to clamp an object so as to prevent motion. In electronic engineering, actuators ACTT, are a subdivision of transducers. They are devices which transform an input signal (mainly an electrical signal) into motion. Specific examples are Electrical motors, pneumatic actuators, hydraulic pistons, relays, comb drive, piezoelectric actuators, thermal bimorphs, Digital Micromirror Devices and electroactive polymers. Motors are mostly used when circular motions are needed, but can also be used for linear applications by transforming circular to linear motion with a bolt and screw transducer. On the other hand, some actuators are intrinsically linear, such as piezoelectric actuators. In virtual instrumentation actuators and sensors are the hardware complements of virtual instruments. Computer programs of virtual instruments use actuators to act upon real world objects.UNC Chapel HillD. ManochaActuatorsLocomotionManipulationUNC Chapel HillM. C. LinActuatorsLocomotionManipulationUNC Chapel HillD. ManochaLocomotionLegsWheelsOther exotic meansUNC Chapel HillD. ManochaLegsTwo legs seems the most obvious configuration–but in fact balance is an incredibly difficult problem•e.g. the Honda Humanoid Project–need knees, ankles and hips in order to move around–two legs are inherently unstable: difficult to stand stillSix legs are much easier to balance and move–stable when not moving–can work with simple cams and rigid legs–Brooks et al. (1989) evolved the walking Genghis robotUNC Chapel HillD. ManochaWheelsAny number of wheels is possible–there are many different configurations that are usefulTwo individually driven wheels on either side–usually with one or more idler wheels for balance–independently driven wheels allows zero turning radius•one wheel drives forwards, one wheel drives backwardsRear wheel drive, with front wheel steering–the vehicle will have a non-zero turning radius –for two front wheels, turning geometry is complex–rear wheels need a differential to prevent slippage4WD is possible, but it is even more complexUNC Chapel HillM. C. LinExotic Wheels & TracksTracks can be