In kinematics, absement (or absition) is a measure of sustained displacement of an object from its initial position, i.e. a measure of how far away and for how long. Absement changes as an object remains displaced and stays constant as the object resides at the initial position. It is the first time-integral of the displacement (the area under a displacement vs. time graph), so the displacement is the rate of change (first time-derivative) of the absement. The dimension of absement is length multiplied by time. Its SI unit is meter second (m·s), which corresponds to an object having been displaced by 1 meter for 1 second. This is not to be confused with a meter per second (m/s), a unit of velocity, the time-derivative of position.
When an object moves, its motion can be described by the integrals of displacement, including absement, absity, abseleration, etc., as well as the derivatives of displacement, including velocity, acceleration, jerk, jounce, etc.
|SI unit||Meter second|
|In SI base units||m·s|
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For example, opening the gate of a gate valve (of rectangular cross section) by 1 mm for 10 seconds yields the same absement of 10 mm·s as opening it by 5 mm for 2 seconds. The amount of water having flowed through it is linearly proportional to the absement of the gate, so it is also the same in both cases.
The word absement is a portmanteau of the words absence and displacement. Similarly, absition is a portmanteau of the words absence and position.
Occurrence in nature
Whenever the rate of change f′ of a quantity f is proportional to the displacement of an object, the quantity f is a linear function of the object's absement. For example, when the fuel flow rate is proportional to the position of the throttle lever, then the total amount of fuel consumed is proportional to the lever's absement.
The first published paper on the topic of absement introduced and motivated it as a way to study flow-based musical instruments, such as the hydraulophone, to model empirical observations of some hydraulophones in which obstruction of a water jet for a longer period of time resulted in a buildup in sound level, as water accumulates in a sounding mechanism (reservoir), up to a certain maximum filling point beyond which the sound level reached a maximum, or fell off (along with a slow decay when a water jet was unblocked). Absement has also been used to model artificial muscles, as well as for real muscle interaction in a physical fitness context. Absement has also been used to model human posture.
As the displacement can be seen as a mechanical analogue of electric charge, the absement can be seen as a mechanical analogue of the time-integrated charge, a quantity useful for modelling some types of memory elements.
In addition to modeling fluid flow and for lagrangian modeling of electric circuits (Jeltsema 2012), absement is used in physical fitness and kinesiology to model muscle bandwidth, and as a new form of physical fitness training. In this context, it gives rise to a new quantity called actergy, which is to energy as energy is to power. Actergy has the same units as action (joule-seconds) but is the time-integral of total energy (time-integral of the Hamiltonian rather than time-integral of the Lagrangian).
Fluid flow in a throttle:
A vehicle's distance travelled results from its throttle's absement. The further the throttle has been opened, and the longer it's been open, the more the vehicle's travelled.
Relation to PID controllers
PID controllers are controllers that work on a signal that is proportional to a physical quantity (e.g. displacement, proportional to position) and its integral(s) and derivative(s), thusly defining PID in the context of Integrals and Derivatives of a position of a control element in the Bratland sense
depending on the type of sensor inputs, PID controllers can contain gains proportional to position, velocity, acceleration or the time integral of position (absement)…— Bratland et al.
Example of PID controller (Bratland 2014):
- P, Position;
- I, Absement;
- D, Velocity.
Just as displacement and its derivatives form kinematics, also displacement and its integrals form "integral kinematics" (Janzen et al. 2014), giving rise to the ordered list of n-th derivatives of displacement:
Absement and absementom
Recent work in mechanics and memristors and memcapacitors further builds on the concept of absement, and assigns it the letter a, and makes extensive use of plots such as the graph of absement as a function of displacement:
... amplitude of the sinusoidal displacement with period , and is the value about which the analytic absement oscillates.
- (See Table 4, "Analytic Displacement and Absement" versus "Piecewise Continuous Displacement and Absement").
Strain absement is the time-integral of strain, and is used extensively in mechanical systems and memsprings:
- Jin-Song Pei, Joseph P. Wright, Michael D. Todd, Sami F. Masri, François Gay-Balmaz (2015). Understanding memristors and memcapacitors in engineering mechanics applications. Springer. Abstract: "for example, a new concept and state variable called “absement,” the time integral of deformation, emerge."
- Dimitri Jeltsema (2012). Memory Elements: A Paradigm Shift in Lagrangian Modeling of Electrical Circuits. arXiv:1201.1032. Abstract: "Although time-integrated charge is a somewhat unusual quantity in circuit theory, it may be considered as the electrical analogue of a mechanical quantity called absement."
- Maya Burhanpurkar. Absement: Direct Evidence of the Time-Integral of Distance. Canada-Wide Science Fair 2014.
- "Absement, displacement, and velocity-sensitive music keyboard in which each key is a water jet", by Mann, Janzen, and Post, In Proceedings of the 14th annual ACM international conference on Multimedia, pp. 519-528. ACM, 2006.
- Amarashiki (2012-11-10). "LOG#053. Derivatives of position". The Spectrum Of Riemannium. Retrieved 2016-03-08.
- ROBUST CONTROL LAW FOR PNEUMATIC ARTIFICIAL MUSCLES, Jonathon E. Slightam and Mark L. Nagurka, Proceedings of the ASME/Bath 2017 Symposium on Fluid Power and Motion Control, FPMC 2017, October 16-19, 2017, Sarasota, USA
- Effectiveness of Integral Kinesiology Feedback for Fitness-based Games, Steve Mann, Max Lv Hao, Ming-Chang Tsai, Maziar Hafezi, Amin Azad, and Farhad Keramatimoezabad, 2018 IEEE Games, Entertainment, Media Conference (GEM), pages 43-50
- Postural strategy for mediolateral weight shifting in healthy adult, J Tousignant, C Cherriere, A Pouliot-Laforte, É Auvinet, Gait & Posture, 2018 - Elsevier
- "Actergy as a Reflex Performance Metric: Integral-Kinematics Applications", Janzen etal., in Proceedings of the IEEE GEM 2014, pp. 311-2. doi:10.1109/GEM.2014.7048123
- "Integral Kinematics (Time-Integrals of Distance, Energy, etc.) and Integral Kinesiology", by Mann etal, in Proceedings of the IEEE GEM 2014, pp. 270-2.
- Bratland, Magne, Bjørn Haugen, and Terje Rølvåg. "Modal analysis of active flexible multibody systems containing PID controllers with non-collocated sensors and actuators." Finite Elements in Analysis and Design 91 (2014): 16-29.