Gimbals & Pointing Mechanisms

« Back

Interactive G35 Gimbal Model

Applications

  • Antenna Gimbals
  • Thruster Gimbals
  • Solar Array Drives
  • Laser Communications
  • Robotics

Procurement Advantage

NEA's customer-centric philosophy has been to create a modern high performance actuator designed for ease of manufacture so critical cost and schedule targets can be met. The design was developed in concert with major spacecraft prime contractors who aided in the development through sharing of technical requirements as well as programmatic cost and schedule goals.

NEA’s program team has focused on these key programmatic objectives in the development of this family of products:

  • Design to Cost
  • Reduced Lead Time
  • Minimize Risk

Interactive P35 Actuator Model

Overview

Introducing a modern range of actuators specifically designed for precision spacecraft pointing applications. NEA's engineering team has assembled the technical requirements of prime contractors around the world and built a family of actuators that meets and in many cases far exceeds their combined requirements.

Engineering Advantage

NEA’s electromechanical engineering team have over 45 years of experience in the spacecraft actuator field and understand the concerns of engineers that specify these devices. To simplify the engineering specification and procurement process NEA has focused on the following areas:

  • Documentation
  • Scalable Modular Design
  • Analysis
  • Qualification
  • Heritage

Scalable Modular Design

NEA engineers have taken a "no compromise" approach to the development of our spacecraft actuator line of devices. Our devices are conceived, developed, analyzed and tested to be the best in class.

NEA has conceived the P35 precision pointing mechanism as the first in a range of devices all using a common design philosophy. The design has been planned up front to be scalable allowing NEA’s considerable investments in analytical models, test equipment and even documentation to be capitalized over the entire product line.

The standardized designs also offer flexibility through a careful modular approach. Two different transmission modules and two different motor modules can be combined to create four possible actuator configurations. The standard telemetry module provides redundant course and fine potentiometers, however, other telemetry modules are available. The actuator modules can be combined with gimbal brackets to create a complete multi-axis pointing platform.

Analytical Correlation

NEA’s electromechanical actuator engineering team has developed a set of standardized analytical models to cover all aspects of the pointing mechanism performance. NEA understands and appreciates that our customer’s engineers are required to verify margins and analysis methods. This is why our analysis tools are world class and our methods and results are well documented for review by our customer counterparts.  

Heritage

NEA pointing mechanisms are based on an optimization of heritage components that all have a history of successful use in long life spaceflight applications.

Design Features

Some of the key design features of NEA’s pointing mechanisms include:

  • Single Axis and Gimbal Configurations
  • Very fine step angles
  • High stiffness output bearings
  • Advanced motor technology
  • Integral thermal monitoring and control
  • Modular Telemetry Options
  • Electrically Redundant
  • Custom Adjustable Stops and Travel Ranges
  • Optional Twist Capsules
  • Optional Rotary Coaxial Joints
  • Optional Stowed Cam Stops

Very Fine Step Angles

Many applications that are concerned with torque disturbance or need higher pointing precision often are driven to micro-stepping.  Micro-stepping can provide very fine step angles, however, it requires 100% duty cycle at all times to maintain rotor position resulting in high power usage and potential thermal dissipation problems.

NEA pointing mechanisms are available with either a 0.0075° output step angle and or a ~0.0024° for very fine positioning and low torque disturbance without the need for micro-stepping.

High Stiffness Output Bearings

NEA’s pointing mechanisms offer high stiffness and load capacity in the output bearing arrangement relative to other similar devices on the market. This ability is achieved all while maintaining a mean Hertzian contact stress of less than 2,310 MPa (335 ksi) under all load conditions for quiet running bearings

Advanced Motor Technology

NEA analyzes and designs all of our motors in-house using advanced state-of-the-art three dimensional magnetic finite element analysis. Our analytical models accurately predict end unit performance and provide the underlying foundation for our torque margins and dynamic simulation models. In-house motor testing is performed at the motor component level on every motor we build, with the results being compared against the analysis to verify the model and also allow capture of out of family performance.

Our precise models allow for performance optimization, weight reduction and in some cases the elimination of rare earth materials that drive cost. The motor configurations used in our pointing mechanisms use far fewer components than most motors used on competitive products resulting in increased reliability, reduced manufacturing time, lower cost and better step accuracy. The additional performance our motors achieve allow us to offer superior performance in a smaller envelope.

Integral Thermal Monitoring and Control

NEA pointing mechanisms include redundant heaters and thermistors embedded in the structure.  The components are mounted to a structural web that is in close proximity to the input bearings.  The close proximity of the thermal control system allows for efficient heating of the components that are most likely to cause degraded torque performance at low temperatures due to lubricant viscosity changes. 

This eliminates the need for external active thermal control, reduces power consumption and protects the thermal control components from damage due to mishandling of the actuator during integration.

Optional Components

NEA Pointing Mechanisms can also be integrated with several optional components to provide a complete gimbal or solar array drive assembly.

Adjustable End of Travel Stops

In limited travel applications NEA attaches hard stops to the features already provided on the actuator mounting flange to limit travel to the desired angles. Hard stops can be customized to provide very precise end of travel angles as required.

Another option is the integration of cam stops that allow the actuator to be stowed for launch beyond the normal travel angle. Once the actuator is deployed into the travel range it is prevented from returning to the stow angle and limited by the passive cam stop to the operational travel range.

Twist Capsules

In limited rotation applications where a service loop will not work NEA can provide a custom twist capsule assembly that can carry both power and signals over the rotating joint. Twist capsules can be built to rotate over 360° of travel and can carry up to several hundred transmission lines. Twist capsules feature flexible circuits that roll within an aluminum housing and have connectors on each side of the rotating interface. Twist capsules of this design have a history of successful use in long life space applications.

Slip Rings

In continuous rotation applications that require power and signals be carried over the rotating interface NEA can integrate our pointing mechanisms with slip ring modules. 

Rotary Coaxial Joints

For antenna pointing applications that require coax be carried over the rotating interface NEA can provide an optional rotary coaxial joint should a service loop not be acceptable for the application.

Telemetry Options

The baseline pointing mechanism features a modular primary and coarse axis redundant potentiometers that provide voltage telemetry over the entire 360° of travel. For some applications, changes to the telemetry angle may be desired. This can be accommodated through the use of a custom potentiometer element within the potentiometer module.

Other applications may require the use of an optical encoder or resolver. These options can also be provided easily due to the modular nature of the device.

Gimbal Brackets

NEA can integrate two or more standard pointing mechanism actuators with brackets to create a multi-axis gimbal that is compliant with customer supplied gimbal specification stiffness and mechanical interface requirements. 

Model P35 Actuator Technical Specifications

Parameter
Units
P35
P35+
P35L
P35L+
Output Step Size
deg
0.0075
0.00241
0.0075
0.00241
Motor Phases
 
3
3
4
4
Nominal Voltage
V
28
28
70
70
Resistance (nom)
Ohms
61.5
61.5
323
323
Power (max)2
W
27.4
27.4
22.6
22.6
Torsional Stiffness (min)
N-m/rad
In·lb/rad
28250
250,000
28250
250,000
28250
250,000
28250
250,000
Unpowered Holding Torque (min)
N-m
In·lb
11.3
100
34
300
11.3
100
34
300
Powered Holding Torque (min)
N-m
In·lb
56.5
500
147
1,300
56.5
500
147
1,300
Maximum Speed3
deg/sec
1.5
0.50
1.5
0.50
Non-operational Temperature Range
°C
-100 to 150
-100 to 150
-100 to 150
-100 to 150
Operational Temperature Range4
°C
-50 to 105
-50 to 105
-50 to 105
-50 to 105
Mass
kg
lb
1.8
4.0
1.8
4.0
1.8
4.0
1.8
4.0
Actuator Data Sheet   P35
Gimbal Data Sheet   G35
CAD Model5    P35 CAD Models
Notes:
1Angle Approximate
2Dependent on duty cycle
3For no-load operation
4Operational temperature range is dependent on the load and inertia applied as torque margins change with temperature
5CAD Model - Subject to change, verify latest configuration with NEA Applications Engineer