  Lego is a well-known platform for prototyping pixelized objects. However,
robotic Lego prototyping (i.e., manipulating Lego bricks) is challenging due to
the tight connections and accuracy requirements. This paper investigates safe
and efficient robotic Lego manipulation. In particular, this paper reduces the
complexity of the manipulation by hardware-software co-design. An end-of-arm
tool (EOAT) is designed, which reduces the problem dimension and allows large
industrial robots to manipulate small Lego bricks. In addition, this paper uses
evolution strategy to optimize the robot motion for Lego manipulation.
Experiments demonstrate that the EOAT can reliably manipulate Lego bricks and
the learning framework can effectively and safely improve the manipulation
performance to a 100% success rate. The co-design is deployed to multiple
robots (i.e., FANUC LR-mate 200id/7L and Yaskawa GP4) to demonstrate its
generalizability and transferability. In the end, we show that the proposed
solution enables sustainable robotic Lego prototyping, in which the robot can
repeatedly assemble and disassemble different prototypes.
