2020-present
GOAT Gripper
GOAT is a rigid, underactuated gripper designed for the uncertainty of free-climbing: irregular holds, imperfect toe placement, and contacts that rarely arrive on the gripper's centerline.
Its whippletree mechanism adds a passive degree of freedom, mechanically balancing the fingers around an object while a single input closes the gripper. The original design was optimized against both kinematic coverage and grasping force, then developed into spine-enhanced and pneumatic C-GOAT variants for SCALER.
Research focus
- Published at IEEE/RSJ IROS, 2021
- Mechanically adaptive whippletree linkage
- Multi-objective mechanism optimization
- Spine and dry-adhesive fingertips
- Seven grasping modes with C-GOAT
Project story
Images and demonstrations
9 media items
01 / Mechanical intelligence
The optimized linkage and the passive adaptation visible in the first prototype.
The dc-actuated gripper uses spine arrays for rough terrain; the pneumatic C-GOAT uses curved dry-adhesive fingers for fast, multi-modal grasping.
01Whippletree mechanism
A single force input is distributed through the linkage while passive motion lets the fingertips settle around off-axis geometry.
Documentation
02Prototype open above a climbing hold
Documentation
03Prototype adapting to an irregular hold
The linkage passively balances after the first fingertip contacts the off-center object.
Documentation02 / From GOAT to C-GOAT
Faster actuation and new fingertip geometries expand a single mechanism into seven grasping modes.
A high-pressure pneumatic actuator trades sensing and payload simplicity for substantially faster grasping.
- C-shaped fingers
- Dry-adhesive contact surface
GOAT manipulation demonstration
Motion studySeven-mode grasping
Pinch, off-axis pinch, envelope, pocket, clamp, sidepull, and hook grasps extend one mechanism across varied climbing geometry.
Motion study03 / On the wall
The gripper becomes part of SCALER's whole-body loco-grasping system.
SCALER uses its limbs and body to create the additional force needed to stabilize a difficult plate contact.
Vertical climbing under payload
Spine-enhanced GOAT grippers support SCALER during a vertical climb with a 3.4 kg payload.
Motion studyDesigned against the terrain
The IROS study turns a gripper-design problem into a task model. Bouldering-hold dimensions define the target environment, while the objective balances graspable kinematic range with the force needed to keep a climbing robot attached.
83.2% theoretical coverage
The optimized linkage covers the dense region of the modeled hold distribution across a 38.02-128.5 mm width range.
79.2% experimental graspability
Testing across 48 unique bouldering holds in two orientations showed adaptation to varied geometry and off-axis placement.
13.3 N design threshold
Pull-force evaluation linked the mechanism's geometry to the minimum load required by the climbing robot.
Single-actuator multimodality
The later C-GOAT configuration realizes seven distinct contact strategies with one actuator.
Two fingertip systems
Spine arrays
Spring-loaded steel spines engage microcavities in rock, concrete, and climbing holds while preserving rigid fingertip support.
C-shaped dry adhesive
Curved fingers create pinch, envelope, clamp, pocket, sidepull, and hook contacts for slippery bars and thin plates.
Robot platform
Built into SCALER
GOAT supplies the adaptable contact; SCALER couples it to articulated limbs, a shifting torso, force control, and climbing gaits.
Explore the SCALER projectPublications & related research
GOAT gripper paper (IROS 2021) →SCALER paper (IEEE T-RO 2025) →