Vertical take off and landing unmanned aerial vehicle (UAV) comprising a multi-propeller propulsion system (“the system”), an outer protective cage surrounding the system, an autonomous power source, a sensing system, and a control system. The sensing system has an orientation sensor and a displacement sensor. The system has at least two propellers spaced apart in a non-coaxial manner. The control system controls the flight or hovering of the UAV. The control system reverses thrust on at least one propeller distal from a point of contact with an obstacle while controlling a motor of a proximal propeller from the contact point to generate lift, the thrust of the distal and proximal propellers being controlled to exert lift on the UAV to counteract gravitational force thereon and apply a moment of rotation about the point of contact to stabilize the position of the UAV or to counteract torque resulting from inertia.