Linear magnetorheological brake with serpentine flux path as a high force and low off-state friction actuator for haptics

Abstract

In robotics and haptics, actuators that are capable of high force output with compact size are desired for stable and stiff interfaces. Magnetorheological brakes are viable options for such implementations since they have large force-to-volume ratios. Existing linear magnetorheological brakes have limited strokes, are relatively large, and have high off-state friction forces mainly due to the piston-cylinder internal design. The main contribution of this research is a new alternative internal design for linear magnetorheological brakes. The proposed approach uses the serpentine flux path concept to eliminate the piston-cylinder arrangement. It leads to significantly less off-state friction and infinite stroke. To the best of our knowledge, this is the first such linear magnetorheological brake. Our new brake can produce 173-N force. In comparison, a conventional linear magnetorheological brake with the same size can only produce about 27-N force. Our results showed that the ratio of the off-state friction force to the maximum force output in the prototype linear brake is about 3% compared with more than 10% for most similar devices in the literature and 27% for a commercial brake. At the same time, the compactness was improved as our prototype is about half the size of a commercially available product.

A linear magnetorheological brake with multipole outer coil structure for high on-state and low off-state force outputs

“…The proposed multipole outer coil linear MR brake design also needs to be compared with other linear brakes in the literature. To this end, the evaluation criteria proposed in [15] were used and Table 4 was created. These evaluation criteria are the cross-sectional area, stroke, maximum force, off-state force, ratio of maximum force to off-state force, required current at maximum force, and power consumption at maximum force.…”

“…However, this design feature also leads to high off-state forces, even if the MR fluid is not activated. The drawback of the conventional design was illustrated by Alkan et al [15]. Off-state force due to the pressure difference was calculated as 71 N for Li et al's design at 30 mm/s [9].…”

“…Through the linear MR brake design, applied with the serpentine flux path concept, Alkan et al achieved 173 N of maximum force and 5.4 N off-state friction. Its ratio of maximum force to off-state force is about 32 [15].…”

“…Alkan et al first applied the shear mode braking principle by using the serpentine flux path concept on linear MR brakes [15]. The serpentine flux path concept was first introduced by Blake and Gurocak for rotary MR brakes [16].…”

Design of a novel magnetorheological damper with internal pressure control

“…owadays, there are several industrial applications in which magnetorheological fluids (MRFs) are used [1][2][3]. In particular, this paper focuses on the optimal design methodology for magnetorheological dampers (MRDs).…”