A robot (100, 800, 1100, 1200, 1400, 1600, 2200, 2300, 2400, 2500, 2600, 3300) capable of addressing various obstacles and comprising: a chassis (140, 301, 310, 501, 801, 1601, 3202) supporting a skid steered drive (110, 1610, 2202, 2204, 3310) and having a leading end (140A, 301A), a trailing end (140B, 301B), and a chassis center of gravity (chassis CG) between the leading and trailing ends (140A, 140B, 301A, 301B); a set of driven flippers (130, 302, 502, 602, 802, 1602), each flipper having a distal end (130A, 302A), a pivot end (130B, 302B), and a flipper center of gravity (flipper CG) between the distal and pivot ends (130A, 130B, 302A, 302B) of the flippers, each flipper (130, 302, 502, 602, 802, 1602) being pivotable about a first pivot axis (15, 315) common with a drive axis near the leading end (104A, 302A) of the chassis (140, 301, 310, 501, 801, 1601, 3202); a neck (305, 805, 1605, 2210) having a distal end, a pivot end, and a neck center of gravity (neck CG) between the distal and pivot ends (305A, 305B) of the neck (305, 805, 1605, 2210), the neck (305, 805, 1605, 2210) pivotable about a second pivot axis substantially at the leading end (140A, 301A) of the chassis (140A, 301A); and a sensor head (303, 803, 1603, 2206) pivotally coupled to the neck (305, 805, 1605, 2210), the sensor head having a distal end, a pivot end, and a head center of gravity (head CG) between the distal and pivot ends (303A, 303B) of the sensor head (303, 803, 1603, 2206); wherein the chassis, flippers, neck and head: (i) have a combined center of gravity (combined CG, 364, CG1, CG50) disposed in a forward-rearward sense between the distal and pivot ends (130A, 130B, 302A, 302B) of the flippers (130, 302, 502, 602, 802, 1602) when the flippers are in a stowed position with their distal ends (130A, 302A) between the leading and trailing ends (140A, 140B, 301A, 301B) of the chassis (140, 301, 310, 501, 801, 1601, 3202), and (ii) are each independently movable between a first position and a second position to reposition the combined center of gravity (combined CG, 364, CG 1, CG50) for negotiating an obstacle. a chassis (140, 301, 310, 501, 801, 1601, 3202) supporting a skid steered drive (110, 1610, 2202, 2204, 3310) and having a leading end (140A, 301A), a trailing end (140B, 301B), and a chassis center of gravity (chassis CG) between the leading and trailing ends (140A, 140B, 301A, 301B); a set of driven flippers (130, 302, 502, 602, 802, 1602), each flipper having a distal end (130A, 302A), a pivot end (130B, 302B), and a flipper center of gravity (flipper CG) between the distal and pivot ends (130A, 130B, 302A, 302B) of the flippers, each flipper (130, 302, 502, 602, 802, 1602) being pivotable about a first pivot axis (15, 315) common with a drive axis near the leading end (104A, 302A) of the chassis (140, 301, 310, 501, 801, 1601, 3202); a neck (305, 805, 1605, 2210) having a distal end, a pivot end, and a neck center of gravity (neck CG) between the distal and pivot ends (305A, 305B) of the neck (305, 805, 1605, 2210), the neck (305, 805, 1605, 2210) pivotable about a second pivot axis substantially at the leading end (140A, 301A) of the chassis (140A, 301A); and a sensor head (303, 803, 1603, 2206) pivotally coupled to the neck (305, 805, 1605, 2210), the sensor head having a distal end, a pivot end, and a head center of gravity (head CG) between the distal and pivot ends (303A, 303B) of the sensor head (303, 803, 1603, 2206); wherein the chassis, flippers, neck and head: (i) have a combined center of gravity (combined CG, 364, CG1, CG50) disposed in a forward-rearward sense between the distal and pivot ends (130A, 130B, 302A, 302B) of the flippers (130, 302, 502, 602, 802, 1602) when the flippers are in a stowed position with their distal ends (130A, 302A) between the leading and trailing ends (140A, 140B, 301A, 301B) of the chassis (140, 301, 310, 501, 801, 1601, 3202), and (ii) are each independently movable between a first position and a second position to reposition the combined center of gravity (combined CG, 364, CG 1, CG50) for negotiating an obstacle. (i) have a combined center of gravity (combined CG, 364, CG1, CG50) disposed in a forward-rearward sense between the distal and pivot ends (130A, 130B, 302A, 302B) of the flippers (130, 302, 502, 602, 802, 1602) when the flippers are in a stowed position with their distal ends (130A, 302A) between the leading and trailing ends (140A, 140B, 301A, 301B) of the chassis (140, 301, 310, 501, 801, 1601, 3202), and (ii) are each independently movable between a first position and a second position to reposition the combined center of gravity (combined CG, 364, CG 1, CG50) for negotiating an obstacle.