Fig. 1: Lightweight knee exoskeletons and motion task and data collection.

a Motion tasks composed of squatting down to pick up an object on the floor and climbing a step. Each motion was asked to be conducted at a different place, and the participants walked there. b Knee exoskeletons. This robot consists of a carbon fiber structure and features a highly responsive joint driven by a pneumatic artificial muscle actuator. c Sensors for a model of assist action sequence and their measurement locations. d EMG locations for measuring muscle load around the knee joint in a real-time exoskeleton robot control experiment. These EMGs are also used for the EMG-based methods.