Actually higher degree of freedom arms with 6-7 DOF have simpler kinematics and are easier to program, in general. This is especially the case if you're using

Actually higher degree of freedom arms with 6-7 DOF have simpler kinematics and are easier to program, in general. This is especially the case if you're using sensing and a lightly unstructured task. An end effector pose has 6 DOF (3 translation, 3 rotation). A robot with fewer than 6 DOF can't physically reach all poses in its task space, so if sensing says go here, the kinematics will often say it can get close, but not exactly. A robot with exactly 6 DOF can usually reach all poses in its task space, with a catch. Typically there are only a discrete number of joint configurations for a given pose (like 4 or 8). Thus, if you want to reach a certain pose but all joint configurations are in collision then you are in trouble. Adding just 1 more DOF, making it a 7 DOF arm, ensures that the arm can generally reach any pose with an infinite number of configurations, the last dimension used to plan avoiding collision. If you use motion planning and sensing for all of this, instead of something like a teach pendant where you carefully set all of the desired poses manually, then higher DOF is easier.