Spacecraft Systems · On-Orbit Servicing

7-DOF Robotic Arm End Effector
with 48 mm Docking Interface
for Satellite Servicing

Design and development of a parametric CAD model of a kinematically redundant 7-DOF robotic manipulator with an adaptive four-finger end effector, compatible with a compact 48 mm docking interface — targeting on-orbit servicing, life-extension, and active debris removal applications.

Institution RV College of Engineering, Bengaluru
Department Aerospace Engineering
Scale Factor 1 : 100 (Canadarm2-inspired)
Configuration 7-DOF Serial Kinematic Chain
Space Robotics 7-DOF Manipulator 48 mm Docking Interface Parametric CAD On-Orbit Servicing Active Debris Removal IDSS / IBDM Adaptive End Effector
7-DOF
Kinematic Chain
176mm
Maximum Reach
48mm
Docking Interface
±7mm
Radial Misalignment Tolerance
60%
Mass Reduction (Boom)
Paper Abstract

Research Overview

Abstract

Robotic manipulators and docking mechanisms are becoming central elements of modern space missions, particularly in the context of on-orbit servicing, life-extension, and active debris removal. This paper presents both the theoretical foundations and a practical CAD implementation of a 7-DOF robotic arm end effector compatible with a compact 48 mm docking interface. The work integrates historical developments, current standards, and recent research on space manipulators with a detailed parametric model inspired by Canadarm2 architecture. The CAD model demonstrates key features including multi-axis articulation, thermal protection systems, cable routing, and an adaptive four-finger claw end effector capable of controlled gripping motion. Based on literature review and preliminary design work, the paper outlines functional requirements and provides a concrete foundation for laboratory-scale satellite servicing demonstrations suitable for small satellites and educational contexts.

Index Terms
space robotics end effector docking mechanism satellite servicing on-orbit operations small satellites CAD modeling 7-DOF manipulator IDSS IBDM
Kinematic Design

7-DOF Joint Configuration

A serial kinematic chain providing redundancy for singularity avoidance, obstacle clearance, and optimal posture selection while maintaining end effector position and orientation.

JOINT 01
Shoulder Yaw
Base azimuthal rotation
±75°
JOINT 02
Shoulder Pitch
Primary vertical positioning
15° – 65°
JOINT 03
Shoulder Roll
Upper arm axial rotation
±17°
JOINT 04
Elbow Pitch
Reach extension / retraction
−115° – −25°
JOINT 05
Elbow Roll
Forearm axial rotation
±12°
JOINT 06
Wrist Pitch
Approach angle control
5° – 45°
JOINT 07
Wrist Yaw
Final alignment adjustment
±35°
Motion Planning

Five-Phase Capture Sequence

Validated through parametric animation across all joints, confirming collision-free operation with smooth velocity profiles throughout.

Phase 01
0–25%
Approach
Shoulder yaw 0°→75°, pitch 15°→65°, elbow extends, claw opens to 7°
Phase 02
25–40%
Alignment
Fine positioning via wrist joints, claw begins closing to 10°
Phase 03
40–55%
Capture
Claw closes to 15°, proximity sensors activate, target engaged
Phase 04
55–65%
Secure
Final grip to 16.5°, force sensors confirm adequate retention load
Phase 05
65–100%
Retract
Return to initial configuration, claw releases to 5° open
Structural Architecture

Boom Design & Structural Features

Hollow cylindrical construction mimicking space-qualified truss design — aluminium primary structure with carbon fibre reinforcement on critical load paths.

Upper Arm Segment
  • Length107 mm
  • Outer Diameter35 mm
  • Inner Diameter29 mm
  • Wall Thickness3 mm
  • Internal Ribs6 ribs with lightening holes
  • CF Longerons4 at 45° intervals for axial stiffness
  • Cable Routing Ports120° spacing for power / signal harness
Forearm Segment
  • Length107 mm
  • Outer Diameter30 mm
  • Inner Diameter25 mm
  • Wall Thickness2.5 mm
  • Internal Ribs6 ribs with lightening holes
  • CF Longerons4 at 45° intervals for axial stiffness
  • Mass Reduction~60% vs. solid cylindrical section
Base Platform
  • FootprintHexagonal, 140 mm diameter
  • Platform Height30 mm with internal volume for power and control electronics
  • Central Mounting Pillar60 mm diameter, mates with Joint 1 housing
  • Mounting Bolts8 positions on 115 mm bolt circle diameter
  • Cable Routing6 radial channels at 60° spacing in platform edges
  • Support Feet3 feet, 12 mm below base, 24 mm diameter contact pads
  • Mass Reduction~25% via weight-reduction pockets on base surface
Terminal System

Adaptive Four-Finger End Effector

A centrally driven claw mechanism with planetary gear synchronisation, integrated sensing, and a 62 mm internal capture diameter — accommodating the 48 mm docking target with ±7 mm radial misalignment tolerance.

Mechanical Architecture

Four fingers driven by a single central motor through a planetary gear system ensuring synchronised, uniform grip force distribution across all fingers. The limited 13° angular travel range (5°–18°) delivers controlled, gentle gripping suitable for delicate satellite components.

  • Base Plate Diameter70 mm, 18 mm height
  • Finger Length55 mm pivot to tip
  • Finger Width / Thickness12 mm / 6 mm
  • Closure Range5° (open) to 18° (closed)
  • Angular Resolution0.5° increments

Finger Features

  • Pivot BearingSpherical housing, 6 mm radius, smooth rotation
  • Taper12 mm base → 6 mm tip for confined-space reach
  • Gripping SurfaceSerrated, 5 triangular teeth at 2 mm pitch
  • Fingertip Pad3 mm compliant rubber for delicate surfaces
  • Actuation LinkageBall joint connection to central motor housing

Integrated Sensing & Perception

  • Vision Cameras4 cameras at 90° intervals, 8 mm aperture, visual servoing
  • Proximity Sensors6 sensors (6 mm dia.) on 45 mm radius circle
  • Force Sensing Ring8 strain gauges for grip force measurement
  • Mounting Interface8 holes at 45° spacing on 70 mm base plate

48 mm Interface Integration

  • Internal Capture Dia.62 mm at fully open (5°)
  • Radial Tolerance±7 mm for 48 mm target boss
  • Angular Capture Env.±45° combined wrist pitch and yaw
  • Docking Ring Space70 mm base provides concentric 48 mm ring mounting
Design Parameters

Key Dimensions

Complete dimensional summary of the 1:100 scale parametric CAD model, based on Canadarm2 kinematic architecture.

7-DOF Manipulator CAD Model — Dimensional Reference
Total Degrees of Freedom
7
Maximum Reach (Extended)
176 mm
Base Platform Diameter
140 mm
Base Platform Height
30 mm
Upper Arm Length
107 mm
Upper Arm Outer Diameter
35 mm
Forearm Length
107 mm
Forearm Outer Diameter
30 mm
End Effector Base Diameter
70 mm
Claw Finger Length
55 mm
Finger Closure Range
5° – 18°
Shoulder Joint Housing Dia.
59.4 mm
Shoulder Joint Housing Ht.
51.3 mm
Docking Interface Target
48 mm
Estimated Total Mass
<2.5 kg