A UK-based online grocery retailer called Ocado Technology says it has created a robotic arm capable of safely grasping a wide variety of products, including produce. The robotic arm is a result of a collaboration between Ocado Technology and the Technische Universität Berlin (TUB), and is part of the SoMa project – a EU-funded program for research and innovation in humanoid robotics that aims to devise robotic hands for handling fragile objects without detailed knowledge of object shape.
One of the main challenges of robotic manipulation has been the handling of easily damageable and unpredictably shaped objects such as fruit and vegetable groceries. These products must be handled in a way that does not cause damage or bruising. To avoid damaging sensitive items, the project uses a compliant gripper (i.e. one that possesses spring-like properties) in conjunction with an industrial robot arm.
The variation in shape of the target objects imposes stringent constraints on the design of a suitable gripper. The gripper must be sufficiently versatile to pick a wide variety of products, including Ocado’s current range which includes over 48,000 items.
To avoid damaging sensitive and unpredictably shaped grocery items, the robotic arm uses the principle of environmental constraint exploitation to establish a carefully orchestrated interaction between the hand, the object being grasped, and the environment surrounding the respective item.
An example of a compliant gripper is the RBO Hand 2 developed at TUB. The gripper uses flexible rubber materials and pressurized air for passively adapting its grasps to pick up objects safely. With seven individually controllable air chambers, the anthropomorphic design enables versatile grasping strategies. The hand’s soft, deformable structure makes it robust against blunt collisions and gives it a low impact energy. Passively compliant fingers and a palm decouple contact from the robot arm, stabilizing force control. And the fact that the hand deforms around object shapes simplifies finger control schemes. Researchers say pneumatic actuation makes it easy to create complex hand and actuator geometries.
Due to its compliant design, the robotic hand is highly under-actuated: only the air pressure is controlled, while the fingers, palm, and thumb adjust their shape to the given object geometry (morphological computation). This simplifies control and enables effective exploitation of the environment.
The Ocado Technology robotics team replicated a production warehouse scenario to evaluate the performance of the RBO Hand 2. The team mounted the soft hand on two different robot arms, a Staubli RX160L and a KUKA LBR iiwa14. Both of these arms can operate in the standard position controlled mode; in addition to this, the KUKA provides the capability of demonstrating a certain amount of software-controlled compliance in the arm.
The RBO Hand 2 is controlled using a PneumaticBox. This is a special control system developed to enable fast, real-time control of pneumatic systems. It contains pressure sensors connected via an on-board ADC (12 Bit) as well as a valve array using 5/3 valves and a Beaglebone Black computer board. Valve drivers are connected via GPIO and the Software stack is based on a Ubuntu distribution customized for the Beaglebone Black board. Additionally, the stack contains a real-time control process air server which handles sensor input, valve output, the execution of low-level controllers and timely execution of scheduled signal events.
In December 2016, Ocado commenced operations from its highly automated Andover warehouse which includes hundreds of robots swarming on a grid the size of several football pitches. In addition, Ocado Technology is a coordinator of the SecondHands project, another EU program trying to design a collaborative robot that can learn from and offer assistance to warehouse maintenance technicians in a proactive manner.