A team of Chinese roboticists have developed a wearable robotic backpack which is designed to boost the walking efficiency of its wearer — allowing them to walk further and carry heavier loads for the same energy expenditure.
"Loaded walking with a rucksack results in both gravitational and inertial forces of the load that must be borne by human carriers. The inertial force may be the source of metabolic burden and musculoskeletal injuries," the team writes in the study's abstract. "This paper presents a lightweight backpack with a disturbance observer-based acceleration control to minimize the inertial force."
The design developed by the team is a 5.3kg (around 11.7lbs) backpack carrying a 24V 6.8Ah battery and a 1.2kg (around 2.6lbs) "physical interface" made up of a 100W brushless motor, 500-line optical encoder, linear actuator, ball screw, and two inertial measurement units (IMUs) which is designed to actively move the load in order to match the wearer's gait. To prove the concept, a 19.4kg (around 42.8lbs) dummy payload — a copper block — was added.
"The backpack was evaluated by seven participants walking on a treadmill at 5 km h−1 with a 19.4 kg load," the researchers write. "Three experimental conditions were involved, including walking with a locked load (LOCKED), with an acceleration-controlled load (ACTIVE) using the designed backpack, and walking with the same load using a rucksack (RUCKSACK)."
"Our results showed that the ACTIVE condition reduces the load acceleration by 98.5% on average, and reduce the gross metabolic power by 8.0% and 11.0% as compared to LOCKED and RUCKSACK conditions respectively. The results demonstrate that the proposed active backpack can improve the loaded walking economy compared with a conventional rucksack in level-ground walking."
"Asian people utilized flexible bamboo poles to carry bulky goods, and Romans designed suspended backpacks to carry heavy loads, which show energetic benefits," Professor Caihua Xiong, study co-author, explains of the project's origins in an interview with IEEE Spectrum. "These designed passive carrying tools have the same principle [as ours]."
The paper has been published as early access in the journal IEEE Transactions on Neural Systems and Rehabilitation Engineering, under closed access terms.