Laser pointers and a touch screen: intuitive interfaces for autonomous mobile manipulation for the motor impaired
Young Sang Choi, Cressel D. Anderson, Jonathan D. Glass, Charles C. Kemp · 2008 · Proceedings of the 10th International ACM SIGACCESS Conference on Computers and Accessibility (Assets '08) · doi:10.1145/1414471.1414512
Summary
This paper presents El-E ("Ellie"), a prototype assistive mobile robot designed to help people with severe motor impairments retrieve everyday objects from the floor. The robot features a vertical lift with a 5-degree-of-freedom manipulator arm, stereo and omnidirectional cameras, a laser range finder, and a mobile base. The research team from Georgia Tech and Emory University developed three distinct user interfaces for commanding the robot: a hand-held laser pointer for users with adequate upper-limb strength and dexterity, an ear-mounted laser pointer designed for users with limited upper-limb mobility, and a touch screen interface displaying the robot's camera feed. All three interfaces communicate a 3D location to the robot using the same abstraction — the robot then autonomously navigates to the object, aligns its gripper using computer vision, and picks it up. The study was motivated by interviews with ALS patients who reported frequently dropping objects and having considerable difficulty retrieving them without caregiver help. Eight participants with ALS or primary lateral sclerosis (PLS) were recruited from the Emory ALS Clinic and completed a two-hour experiment involving 134 total trials across all three interfaces, using three everyday objects (a cordless phone, a medicine box, and a plastic bottle) placed at two floor positions.
Key findings
Across all 134 trials, the robot successfully picked up the target object 94.8% of the time, with no participant having prior experience with robots of this kind. Users learned each interface in under 10 minutes. Laser pointer interfaces (both hand-held and ear-mounted) were 69% faster for object selection than the touch screen, with average selection times of 4.85 seconds (ear-mounted), 5.01 seconds (hand-held), and 14.18 seconds (touch screen). However, pointing accuracy and grasping time did not vary significantly across interfaces. User preferences correlated strongly with physical ability: participants with higher ALSFRS-R scores (greater upper-limb mobility) preferred the hand-held laser pointer, while those with less mobility preferred the ear-mounted version. Despite the speed advantage of laser pointers, three participants preferred the touch screen for its ability to manipulate objects outside their line of sight. Satisfaction scores were high across all interfaces (5.50 to 5.61 out of 7), with no significant differences between them. The key architectural insight was that the 3D location serves as a powerful abstraction barrier — any interface that can communicate a 3D position can control the same underlying robotic functionality, enabling a multi-interface approach.
Relevance
This study provides compelling evidence that assistive robots can be made accessible to people with severe motor impairments through thoughtfully designed, multiple interface options. The 3D-location abstraction barrier concept is a significant design principle: by decoupling the user interface from the robotic functionality, new input methods (eye tracking, head movements, brain-computer interfaces) can be added without modifying the robot itself. This mirrors the accessibility principle of separating content from presentation. The finding that no single interface suited all users — and that preference correlated with specific functional abilities — reinforces the importance of offering multiple interaction modalities rather than a one-size-fits-all solution. For accessibility practitioners, the study demonstrates that even users with very limited motor function can independently command complex robotic systems when interfaces are matched to their capabilities. The work also highlights the value of involving the target user population (ALS patients) throughout the design process, from initial needs assessment interviews through controlled experimentation.
Tags: assistive robotics · motor impairment · amyotrophic lateral sclerosis · human-robot interaction · laser pointer interface · touch screen · mobile manipulation · object retrieval