  Since wearable linkage mechanisms could control the moment transmission from
actuator(s) to wearers, they can help ensure that even low-cost wearable
systems provide advanced functionality tailored to users' needs. For example,
if a hip mechanism transforms an input torque into a spatially-varying moment,
a wearer can get effective assistance both in the sagittal and frontal planes
during walking, even with an affordable single-actuator system. However, due to
the combinatorial nature of the linkage mechanism design space, the topologies
of such nonlinear-moment-generating mechanisms are challenging to determine,
even with significant computational resources and numerical data. Furthermore,
on-premise production development and interactive design are nearly impossible
in conventional synthesis approaches. Here, we propose an innovative autonomous
computational approach for synthesizing such wearable robot mechanisms,
eliminating the need for exhaustive searches or numerous data sets. Our method
transforms the synthesis problem into a gradient-based optimization problem
with sophisticated objective and constraint functions while ensuring the
desired degree of freedom, range of motion, and force transmission
characteristics. To generate arbitrary mechanism topologies and dimensions, we
employed a unified ground model. By applying the proposed method for the design
of hip joint mechanisms, the topologies and dimensions of non-series-type hip
joint mechanisms were obtained. Biomechanical simulations validated its
multi-moment assistance capability, and its wearability was verified via
prototype fabrication. The proposed design strategy can open a new way to
design various wearable robot mechanisms, such as shoulders, knees, and ankles.
