Narrow Results

Body-borne load reportedly increases incidence of military-related knee injury by altering trunk and lower limb biomechanics. This investigation determined whether body-borne load impacts lateral trunk flexion during a single-leg cut, and whether greater lateral trunk flexion exaggerates knee abduction biomechanics. Thirty-six participants had trunk and knee biomechanics quantified during a single-leg cut with four body-borne loads (20, 25, 30 and 35kg). To evaluate the impact of load on lateral trunk flexion and its relation with knee abduction biomechanics, peak stance lateral trunk flexion was submitted to a linear mixed model with load (20, 25, 30, and 35kg) and sex (male, female) as fixed effects, and dominant limb peak stance knee abduction joint angle and moment considered as covariates. During the cut, there was a significant sex by load interaction for peak stance lateral trunk flexion ($p=0.038$), and peak stance lateral trunk flexion angle exhibited a significant association with peak stance knee abduction angle ($p<0.001$) and moment ($p=0.014$). Adopting lateral trunk flexion during loaded single-leg cuts may increase knee biomechanics related to ACL injury, but adding load only decreased lateral trunk flexion for female participants and did not further exaggerate knee abduction biomechanics.

The moving torso plays an important role in the dynamics of bipeds like human beings, the exploitation of which is the essential focus of this paper. A design is presented where the torso is actuated to make the biped walk with the required step-length while allowing the legs to move passively. A periodic response excitation is achieved and the motion of the torso is optimized with respect to the external energy input. A working model of the biped is designed and built in which only the torso is actuated and the legs are passive. This laboratory model is used to test and validate the analytical solutions.

Moving the torso laterally in a walking biped robot can be mechanically more torque-efficient than not moving the torso according to recent research. Motivated by this observation, a torque-efficient torso-moving balance control strategy of a walking biped robot subject to a persistent continuous external force is suggested and verified in this paper. The torso-moving balance control strategy consists of a preliminary step and two additional steps. The preliminary step (disturbance detection) is to perceive the application of an external force by a safety boundary of zero moment point, detected approximately from cheap pressure sensors. Step 1 utilizes center of gravity (COG) Jacobian, centroidal momentum matrix and linear quadratic problem calculation to shift the zero moment point to the center of the support polygon. Step 2 makes use of H_∞ controllers for a more stable state shift from single support phase to double support phase. By comparing the suggested torso moving control strategy to the original control strategy that we suggested previously, a mixed balance control strategy is suggested. The strategy is verified through numerical simulation results.

The passive dynamic walker is well known for its success in human mimicry; however, the torso, an important part of humans and human-like biped robot, is usually ignored in the model. In this paper, a fully passive torso is coupled to the passive dynamic walker via two hip torsional springs. The performances of the walker are studied by means of numerical simulation, and the benefits brought by the torso are revealed. Comparisons with the walker without a torso are performed. On a regular slope, the gait's existence and specifications are studied with respect to the slope angle and the spring coefficient. An interesting dynamical phenomenon of having two stable walking cycles is observed, and the differences between them are presented via a parametric study. The ranges of stable walking slopes and gait performances are significantly improved. On an irregular slope, the disturbance rejection ability (DRA) is measured for three types of disturbances. The slope range of stable gait with strong DRA is significantly extended. The walker with a torso is more flexible by adjusting the slope angle, the spring coefficient and its initial state. The unique properties of our model can be utilized to design humanoid robots and walking enhancing equipment.