Mobile Universal Jamming Gripper

Yi-Sheng Lau-Cortes(∗), Daniel Sapiain-Caro, Alexis Fuentealba-Orrego,

and Ricardo Mendoza-Garcia

School of Mechanical EngineeringUniversity of Tarapaca

Arica-Chile(∗) Corresponding author: yisheng.88@gmail.com

1 Introduction

Versatile robotic grasping is a complicated task that an universal jamming grip-per [1] simplifies to a big extent because of its ability to pick up objects ofdifferent shapes with little effort. However, this pioneering gripper has not yetbeen used in mobile manipulators despite its potential to easily pick and trans-port objects elsewhere. In this paper we replicate an universal jamming gripperand make a preliminary design of a mobile base that –together with the gripper–could work as a mobile universal grasping platform at a following stage of ourresearch.

2 Mobile pneumatics - Methods

2.1 Overall robot design

Figure 1: Preliminary design of a mobile universal jamming gripper.

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For the jamming gripper to work, a vacuum is required and can be obtainedeither with a compressor attached to a Venturi pipe or with a vacuum pump.This means that electricity is needed in the robot for the compressor or thepump, and also for the microcontroller and drives. Since these devices haveconsiderable energetic demands, we want to use a small combustion engine topower the device.

For mobility, it has not been yet decided what kind of wheel configurationto utilize. Two types of configurations are being tested: the differential and theomni-directional ones. Depending on the wheels configuration and estimatedweight of the robot, we should select the number and power of DC motors. Thearm design will include 180o servomotors and depending on an estimate of thefinal arm weight, we should calculate the minimum power of the motors for eachlink.

A very preliminar idea of the overall look of the robot is shown in Fig. 1.

2.2 Gripper replication

To replicate the experience of [1], we used silicone, a coffee-filled balloon (Fig.2a), coffee filters, pneumatic hoses, and a hacked fish-tank pressure pump work-ing as a vacuum pump (Fig. 2b). The assembled jamming gripper is shown inFig. 2c.

(a) Coffee-filled balloon. (b) Vacuum Pump. (c) Balloon and pump.

Figure 2: Implementation of an universal jamming gripper.

3 Pneumatic grasping - Results

The jamming gripper of Fig. 2 was tested with great success. Fig. 3 shows thegripper picking up objects of diverse sizes and shapes.

4 Discussions

Whilst this preliminary experiment worked, we had one previous failed at-tempt with a 3D-printed Venturi pipe. Among the problems, we observed leaksthrough the bodies of the 3D-printed parts (a consequence of the solid printing

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(a) Agorex bottle (b) Lego Gear (c) Screwdriver (d) Screw (e) T pneumaticconnector

Figure 3: Jamming gripper in action.

process) and also very little air-flow through the body of the small pipe. Hence,even though this approach was attractive due to the miniaturization possibili-ties, the long times required to grasp any object may prohibit its utilization.

To finish, as jamming makes easier to grasp objects of diverse sizes andshapes, the requirements of the microcontroller controlling the manipulator andfiring the activation of the gripper are reduced considerably; no complex robotvision is needed when there is no need to precisely approach targets.

5 Conclusions and Future Work

We presented a preliminary and very rough design of a mobile base that couldpotentially carry a pneumatic gripper, and we replicated the construction andperformance of an universal jamming gripper in our lab. Considering the avail-able equipment at our laboratory, a vacuum pump seems to be a better optionthan a compressor and a Venturi pipe for on-board generation of vacuum. Thenext step of our research is to decide on wheels and to begin the implementationof the mobile base in parallel to a small robotic arm.

References

[1] J. Amend, E. Brown, N. Rodenberg, H. Jaeger, and H. Lipson, “A posi-tive pressure universal gripper based on the jamming of granular material,”Robotics, IEEE Transactions on, vol. 28, no. 2, pp. 341 –350, April 2012.

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