Franklin Robotics have designed a Solar Powered Weeding Robot called Terthill.
terthill weeding robot
The robot wanders through the veg garden strimming any small plant it comes across. The robot senses and moves away from large plants, or plants which have been protected by special collars. The range of the patch, through which it may work, has to be defined by a barrier which it will sense & move away from.
Terthill is powered by a solar panel. The robot is waterproof which means that it can be left in the garden all the time.
This solar powered weeding robot, Terthill, is not in full production yet, but it is worth looking out for.