Soft pushing operation with dual compliance controllers based on estimated torque and visual force

Abdul Muis, Kouhei Ohnishi

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)


Sensor fusion extends robot ability to perform more complex tasks. An interesting application in such an issue is pushing operation, in which through multi-sensor, the robot moves an object by pushing it. Generally, a pushing operation consists of "approaching, touching, and pushing" (1). However, most researches in this field are dealing with how the pushed object follows the predefined trajectory. In which, the implication as the robot body or the tool-tip hits an object is neglected. Obviously on collision, the robot momentum may crash sensor, robot's surface or even the object. For that reason, this paper proposes a soft pushing operation with dual compliance controllers. Mainly, a compliance control is a control system with trajectory compensation so that the external force may be followed. In this paper, the first compliance controller is driven by estimated external force based on reaction torque observer(2), which compensates contact sensation. The other one compensates non-contact sensation. Obviously, a contact sensation, acquired from force sensor either reaction torque observer of an object, is measurable once the robot touched the object, Therefore, a non-contact sensation is introduced before touching an object, which is realized with visual sensor in this paper. Here, instead of using visual information as command reference, the visual information such as depth, is treated as virtual force for the second compliance controller. Thus, having contact and non-contact sensation, the robot will be compliant with wider sensation. This paper considers a heavy mobile manipulator and a heavy object, which have significant momentum on touching stage. A chopstick is attached on the object side to show the effectiveness of the proposed method. Here, both compliance controllers adjust the mobile manipulator command reference to provide soft pushing operation. Finally, the experimental result shows the validity of the proposed method.

Original languageEnglish
Pages (from-to)518-527+9
JournalIEEJ Transactions on Industry Applications
Issue number5
Publication statusPublished - 2007


  • Artificial marker
  • Compliance controller
  • Mobile manipulator
  • Pushing operation
  • Reaction torque observer
  • Robot vision


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