Hybrid Haptic Device

• Research Background
• With only one kind of actuator, it is difficult to display stable and realistic haptic effects in various situations.
• Since an active actuator and a passive actuator are complementary to each other in various respects, use of both a motor and a brake may lead to better haptic effects.
• Researchers
• Kwon Tae-Bum(Ph.D. course)

• Period of research
  • 2003.03 ~ 2004.02

• Research Output

               

<Photo of the Hybrid Haptic Device (HHD)>

• paper1: Tae-bum Kwon, Jae-Bok Song, Force display using a hybrid haptic device composed of motors and brakes, Mechatronics, Vol. 16, published, pp. 249-257, 2006, 06.
• paper2: Tae-bum Kwon, Jae-Bok Song, Implementation of Virtual Environment Based on Combination of Motors and Brakes, Automation and Systems, pp. 602-608, 2005. 07
• paper3: Tae-Bum Kwon, Jae-Bok Song, force Display Based on Simultaneous Actuation of Motors and Brakes, Proc. of 2004 Int. Conf. on Control, Automation and Systems, pp. 1131-1135, 2004. 08

• Research Objectives
• Design of a new haptic device equipped with active actuators, motors and passive actuators, brakes.
• Analysis of characteristics of each actuator and development of simultaneous actuation method of motors and brakes.
• Development of various haptic effects; some are preferable to single actuator system and others to hybrid actuator system.

• Characteristics of active actuator and passive actuator
• Motor is a typical active actuator and has many advantages such as fast response and facility of control. But it may make the system unstable due to its activity.
• Brake is a typical passive actuator(another typical passive actuator is damper) and has also many advantages such as stable output and high ratio of output/weight. But its respose is slow and it can generate a torque only against the direction of its motion or only against an externally applied torque.

                

                                   <Active actuator vs. passive actuator>

• Structure of hybrid haptic device equipped with motors and brakes
  • 5-bar linkage, pulleys, wires, motors, brakes and force/torque sensor were used.
  • The length of each link and the shape of each pulley were determined for the workspace to be 380mm x 230mm. 
  • Using FME (Force Manipulability Elliosoid) analysis the device was designed to produce the maximum force of more than 80N in all direction over the whole workspace.

                

            <Linkage mechanism for 2-DOF haptic device and its workspace>

• The Maxon 120W BLDC motor along with the speed reducer was used to generate a torque of 4.44Nm. The response time of the motor is 7ms.
• The Ogura particle brake OPB-40N can generate the minimum torque of 2Nm. The response time of the brake is 50ms.
• The output torque of motors and brakes was amplified by a set of pulleys with the 5:1 ratio and wires.

               

            <Linkage mechanism for 2-DOF haptic device and its workspace>

• Application example 1 of HHD: virtual wall contact

                

        <Example of contact with hard wall at high velocity>

• Virtual wall contact is basic but the most important haptic effect.
• In motor only system, the virtual wall is modelled with a spring and a damper. In this research, as shown in Fig. 5, it was modelled with spring, damper and brake.
• When the hard wall with high stiffness is displayed with only motor, it can be unstable easily.
• If a large damping force is generated by motor at the initial contact, the slow response of the brakes can be compensated by the motors whose response is relatively fast. And the virtual wall is displayed stably.

• Demo of HHD in contact with hard wall

• Demo of playing air-hockey game using HHD

- Last updated: 2012. 4. 24