The angular position (attitude) of an implement 25 e.g. a vegetation cutter, which is pivotable about an axis 26 at one end of an articulated arm 17, 18, 22 is controlled by a system which comprises a sensor 32 which generates a first electrical signal corresponding to the angular position of the implement relative to a datum plane, a device 38 for generating a second electrical signal which corresponds to a desired position of the implement 25, and a control circuit 34 operating an actuator 27 in accordance with a difference between the first and second signals.
