Where am I? Sensors and Methods for Mobile Robot Positioning

More documents

Recommendations

Info

62 Part I Sensors for Mobile Robot Positioning in conjunction with any magnetoelastic expansion or contraction of its coating. The output beam from this fiber-optic cable is combined in a light coupler with the output beam from the uncoated reference fiber and fed to a pair of photodetectors. Constructive and destructive interferences caused by differences in path lengths associated with the two fibers will cause the final output intensity as measured by the photodetectors to vary accordingly. This variation is directly related to the change in path length of the coated fiber, which in turn is a function of the magnetic field strength along the fiber axis. The prototype constructed by Lenz [1990] at Honeywell Corporation measured 10×2.5 centimeters (4×1 in) and was able to detect -7 fields ranging from 10 Gauss up to 10 Gauss. Researchers at the Naval Research Laboratory (NRL) have developed a prototype magnetoelastic -5 magnetometer capable of detecting a field as small as 6×10 Gauss [Brizzolara et al., 1989] using the tunneling-tip approach. This new displacement sensing technology, invented in 1982 at IBM Zürich, is based on the measurement of current generated by quantum mechanical tunneling of electrons across a narrow gap (Figure 2.29). An analog feedback circuit compares the measured tunnel current with a desired value and outputs a drive signal to suitably adjust the distance between the tunneling electrodes with an electromechanical actuator [Kenny et al., 1991]. The instantaneous tunneling current is directly proportional to the exponential of electrode displacement. The most common actuators employed in this role are piezoelectric and electrostatic, the latter lending itself more readily to silicon micro-machining techniques. Tip Cantilever Surface Figure 2.29: Scanning tunneling microscopy, invented at IBM Zürich in 1982, uses quantum mechanical tunneling of electrons across a barrier to measure separation distance at the gap. (Courtesy of T. W. Kenny, NASA JPL). The active sense element in the NRL magnetometer is a 10 centimeter (4 in) metallic glass ribbon made from METGLAS 2605S2, annealed in a transverse magnetic field to yield a high magnetomechanical coupling [Brizzolara et al., 1989]. (METGLAS is an alloy of iron, boron, silicon, and carbon, and is a registered trademark of Allied Chemical.) The magnetoelastic ribbon elongates when exposed to an axial magnetic field, and the magnitude of this displacement is measured by a tunneling transducer as illustrated in Figure 2.30. An electrochemically etched gold tip is mounted on a tubular piezoelectric actuator and positioned within about one nanometer of the free end of the METGLAS ribbon. The ribbon and tip are electrically biased with respect to each other, establishing a tunneling current that is fed back to the piezo actuator to maintain a constant gap separation. The degree of magnetically induced elongation of the ribbon can thus be inferred from the driving voltage applied to the piezoelectric actuator. The solenoidal coil shown in the diagram supplies a bias field of 0.85 oersted to shift the sensor into its region of maximum sensitivity.
Chapter 2: Heading Sensors 63 Approach mechanism High voltage amps Tunneling tip piezo It V bias Tunneling tip Magnetostrictive ribbon Electronics feedback Lecroy scope Solenoid coils Quartz tube Figure 2.30: The NRL tunneling-transducer magnetometer employed a 10 cm (4 in) magnetoelastic ribbon vertically supported in a quartz tube [Brizzolara et al., 1989]. Fenn et al. [1992] propose an alternative tunneling-tip magnetoelastic configuration with a -11 predicted sensitivity of 2×10 Gauss, along the same order of magnitude as the cryogenically cooled SQUID. A small cantilevered beam of METGLAS 2605S2, excited at its resonant frequency by a gold-film electrostatic actuator, is centered between two high-permeability magnetic flux concentrators as illustrated in Figure 2.31. Any changes in the modulus of elasticity of the beam will directly affect its natural frequency; these changes in natural frequency can then be measured and directly related to the strength of the ambient magnetic field. The effective shift in natural frequency is rather small, however (Fenn et al. [1992] report only a 6 Hz shift at saturation), again necessitating a very precise method of measurement. 0.7 mm Metglas cantilever Substrate 0.7 mm NS Flux guide Flux guide NS 1or 5 cm Figure 2.31: Top view of the single cantilevered design. (Adapted from [Fenn, et al., 1992].) A second (non-magnetic) cantilever element is employed to track the displacement of the METGLAS reed with sub-angstrom resolution using tunneling-tip displacement sensing as illustrated in Figure 2.32. A pair of electrostatic actuator plates dynamically positions the reed follower to maintain a constant tunneling current in the probe gap, thus ensuring a constant lateral separation between the probe tip and the vibrating reed. The frequency of the excitation signal applied to the reed-follower actuator is therefore directly influenced by any resonant frequency changes occurring in the METGLAS reed. The magnetometer provides an analog voltage output which is proportional to this excitation frequency, and therefore indicative of the external magnetic field amplitude.
Page 2 and 3:
7KH8QLYHUVLW\RI0LFKLJDQ Where am I
Page 4 and 5:
Acknowledgments This research was s
Page 6 and 7:
2.4.2.2 Watson Gyrocompass ........
Page 8 and 9:
6.4 Summary .......................
Page 10 and 11:
INTRODUCTION Leonard and Durrant-Wh
Page 12 and 13: Part I Sensors for Mobile Robot Pos
Page 14 and 15: 14 Part I Sensors for Mobile Robot
Page 30 and 31: CHAPTER 2 HEADING SENSORS Heading s
Page 42 and 43: 6 42 Part I Sensors for Mobile Robo
Page 64 and 65: Excitation actuator Metglas reed Tu
Page 112 and 113:
112 Part I Sensors for Mobile Robot
Page 114 and 115:
Page 116 and 117:
Page 118 and 119:
Page 120 and 121:
Page 122 and 123:
Page 124 and 125:
Page 126 and 127:
Page 128 and 129:
Page 130 and 131:
CHAPTER 5 ODOMETRY AND OTHER DEAD-R
Page 132 and 133:
132 Part II Systems and Methods for
Page 134 and 135:
Page 136 and 137:
Page 138 and 139:
Page 140 and 141:
Page 142 and 143:
Page 144 and 145:
Page 146 and 147:
Page 148 and 149:
Page 150 and 151:
Page 152 and 153:
Page 154 and 155:
Page 156 and 157:
Page 158 and 159:
Page 160 and 161:
Page 162 and 163:
Page 164 and 165:
Page 166 and 167:
Page 168 and 169:
Page 170 and 171:
Page 172 and 173:
Page 174 and 175:
Page 176 and 177:
Page 178 and 179:
R e t r o r e f l e c t i v e m a r
Page 180 and 181:
Page 182 and 183:
Page 184 and 185:
CHAPTER 8 MAP-BASED POSITIONING Map
Page 186 and 187:
Page 188 and 189:
Page 190 and 191:
Page 192 and 193:
Page 194 and 195:
Page 196 and 197:
Page 198 and 199:
Page 200 and 201:
Page 202 and 203:
Page 204 and 205:
Page 206 and 207:
Page 208 and 209:
Page 210 and 211:
Page 212 and 213:
Page 214 and 215:
Page 216 and 217:
Page 218 and 219:
218 Appendices, References, Indexes
Page 220 and 221:
220 Appendices, References, Indexes
Page 222 and 223:
Systems-at-a-Glance Tables Odometry
Page 224 and 225:
Systems-at-a-Glance Tables Global N
Page 226 and 227:
Systems-at-a Glance Tables Beacon N
Page 228 and 229:
Systems-at-a-Glance Tables Landmark
Page 230 and 231:
Page 232 and 233:
Page 234 and 235:
This page intentionally left blank
Page 236 and 237:
REFERENCES 1. Abidi, M. and Chandra
Page 238 and 239:
238 References 31. Boltinghouse, S.
Page 240 and 241:
240 References MOBOT-IV.” Proceed
Page 242 and 243:
242 References 90. Dahlin, T. and K
Page 244 and 245:
244 References 120. Fisher, D., Hol
Page 246 and 247:
246 References 156. Janet, J., Luo,
Page 248 and 249:
248 References 187. Larsson, U., Ze
Page 250 and 251:
250 References 220. Nolan, D.A., Bl
Page 252 and 253:
252 References 249. Sanders, G.A.,
Page 254 and 255:
254 References 278. Turpin, D.R., 1
Page 256 and 257:
256 References 309. EATON - Eaton-K
Page 258 and 259:
258 References 349. SPSi - Spatial
Page 260 and 261:
260 References 380. MacKenzie, P. a
Page 262 and 263:
262 Index AC ..............47, 59,
Page 264 and 265:
264 Index Datums ..................
Page 266 and 267:
266 Index glass ...................
Page 268 and 269:
268 Index lateral-post ............
Page 270 and 271:
270 Index NPN .....................
Page 272 and 273:
272 Index signal ..... 17, 31, 38,
Page 274 and 275:
274 Index Abidi ...................
Page 276 and 277:
276 Index Kak .....................
Page 278 and 279:
278 Index Weiman ..................
Page 280 and 281:
280 Index Video Index This CD-ROM c
Page 282:
282 Index Paper 52 Paper 53 Paper 5
show all

Where am I? Sensors and Methods for Mobile Robot Positioning

Create successful ePaper yourself

Delete template?

Save as template?