Engineering topics
Publications and source records attributed to Brown, T. K..
New control system damps vibrations in rotating equipment with help of phase-locked-loop techniques. Vibrational modes are controlled by applying suitable currents to drive motor. Control signals are derived from sensors mounted on equipment.
Design problems and the solutions adopted for them in the attitude and articulation control subsystem for the Galileo spacecraft are discussed as an illustration of the application of dual-spin control to an interplanetary spacecraft. Following a review of the baseline design of the Galileo system and mission, consideration is given to problems encountered in the areas of autonomous attitude determination, attitude control, spacecraft dynamics and software margins. Design issues raised by subsequent changes in spacecraft configuration are also indicated. It is pointed out that although difficulties associated with control system complexity in a dual-spin interplanetary spacecraft have been satisfactorily resolved for the Galileo mission, the future application of dual spin in interplanetary flight is in doubt.
Galileo is a dual-spin spacecraft designed to deliver a probe to Jupiter and then orbit the planet. The stator, or despun section, contains four flexible modes below 10 Hz and the despun actuator is separated from the inertial sensors by this flexibility. Control loop separation by bandwidth proved unacceptable due to performance requirements. To obtain the desired performance, a control scheme was devised which consists of three parts. First, flexibility damping and control notch filtering are accomplished by phase locked loop techniques. Second, slewing maneuvers are produced by torque profiles which are nonexcitatory to the structure. Finally, a low bandwidth perturbation controller is supplied to remove spacecraft disturbances.
As part of its advanced development work, JPL is developing a Precision Pointing and Tracking System (PPTS) for science platform control on unmanned planetary spacecraft. The PPTS will extend science capabilities on future missions by providing highly accurate (10 arcsec) and stable (0.2 arcsec) pointing of the platform. Key features of the design include closed-loop tracking of target bodies using an optical sensor and decoupling of spacecraft dynamics via high-bandwidth, inertially stabilized control. This paper discusses the analyses and design. Computer simulations were used to establish the feasibility of the design approach and to verify that the performance requirements can be met. A breadboard demonstration of the entire system is expected in late 1980.