Control Systems: Nyquist Stability Criterion

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Questions and Answers

Considering the geopolitical landscape of 7th-century India, which of the following factors most likely contributed to the rise of numerous independent kingdoms after the disintegration of the Gupta Empire?

  • The weakening of central authority exacerbated by invasions and internal power struggles, leading to regional assertion of sovereignty by former Gupta feudatories. (correct)
  • The deliberate dismantling of centralized military infrastructure by the later Gupta rulers to promote local governance.
  • A widespread adoption of a uniform legal code that inadvertently fostered regional autonomy among the administrative divisions.
  • Diminished trade routes due to natural disasters, compelling regions to become economically self-reliant and politically independent.

Given the established feudal structure of ancient Indian kingdoms, which action by Harsha Vardhana would have MOST effectively consolidated his rule and ensured long-term stability across his newly formed kingdom?

  • Implementing a centralized currency system to facilitate trade and reduce regional economic disparities.
  • Reforming the administrative structure to incorporate loyal regional chieftains into a hierarchical system of governance, thus co-opting potential rivals. (correct)
  • Commissioning the construction of extensive irrigation networks to boost agricultural productivity and foster economic dependence on the central authority.
  • Establishing a new, syncretic religious order to unify diverse populations and legitimize his authority.

If the Mantri Parishad's (Council of Ministers) support was crucial for Harsha Vardhana's ascension, what prevailing sociopolitical condition does this detail MOST strongly imply about the nature of monarchical succession in that era?

  • The monarch's power was absolute and unconditional, with the Council's support being purely ceremonial and devoid of any practical implication.
  • The absence of a clear-cut succession law or the existence of multiple legitimate claimants could lead to reliance on the Council's consensus for validation. (correct)
  • The monarch was elected by the Mantri Parishad from among eligible royal family members, making their support a mere formality.
  • Monarchical succession was strictly determined by primogeniture, necessitating the Council's endorsement to circumvent established laws.

Judging from the information available, which of the subsequent developments in Indian history would have been MOST contrary to the political trajectory initiated by Harsha Vardhana?

<p>The proliferation of smaller, regional kingdoms engaged in frequent internecine conflicts and lacking a centralizing force. (D)</p> Signup and view all the answers

Given the historical context and Harshavardhana's efforts to consolidate power, what strategic advantage would control over both Prayag and Kanauj confer upon a ruler in 7th century India?

<p>Dominating the fertile Gangetic plains and critical transportation arteries, facilitating military mobilization and economic control. (A)</p> Signup and view all the answers

Considering the patterns of dynastic alliances and conflicts during the Post-Gupta period, what strategic imperative MOST likely drove Graha Varman's marriage to Rajyashri of the Pushyabhuti family of Thaneshwar?

<p>Forming a political alliance to counter the rising power of a rival kingdom, thereby preserving the balance of power in the region. (D)</p> Signup and view all the answers

If Ishana Varman adopted the title Maharajadhiraja, what shift in Maukhari dynastic policy does this action MOST likely represent, compared to the preceding three kings who held only the title Maharaja?

<p>A transition from a subordinate or tributary relationship to one asserting sovereign and imperial authority. (B)</p> Signup and view all the answers

Given the prominence of figures like Hieun-Tsang, and assuming patterns of cultural exchange, what impact would the presence of such travelers MOST likely have had on governance under rulers such as Harsha?

<p>Enhanced understanding of foreign political systems and administrative techniques and the ability to use this to improve governance. (C)</p> Signup and view all the answers

Considering the geographical locations and the historical context, what strategic objective would MOST logically explain Prabhakara Vardhan's campaigns against the Hunas, Gurjaras, and other regional powers?

<p>Securing the northern frontiers against external invasions and expanding the dynasty's sphere of influence, ensuring regional hegemony. (B)</p> Signup and view all the answers

If Harsha was reluctant to accept the responsibilities of kingship, yet brought 'a majority of the regions of northern India under his management/control,' what inference can be justifiably drawn regarding the administrative structures in place?

<p>The swift consolidation suggests existing infrastructure facilitated centralization, implying a highly structured bureaucratic tradition. (B)</p> Signup and view all the answers

Considering the context of the 6th century AD, what specific advantage did situating the Pushyabhuti kingdom in Srikanta Janapada (modern Haryana) MOST likely confer upon its rulers?

<p>A strategic position to monitor and control movements along key inland trade routes, extracting revenue and projecting power. (A)</p> Signup and view all the answers

If Sarva Varman's ascension to the throne marked a shift, establishing 'a strong presence of Maukharis in Madhya Desha,' what primary change in geopolitical focus did this likely entail for the Maukhari kingdom?

<p>A shift towards prioritizing control over vital agricultural lands and river systems in the heartland of India. (C)</p> Signup and view all the answers

Supposing the title 'Maharaja' was granted to the first three Maukhari kings, what inherent limitation, in terms of political signaling, would this title impose on their ability to project power and influence compared to rulers claiming titles like 'Maharajadhiraja'?

<p>It prevented them from claiming suzerainty over other rulers, signaling a subordinate or equal status in the regional hierarchy. (C)</p> Signup and view all the answers

Considering the common motivations of ancient rulers, what primary incentive MOST likely drove Ishana Varman to engage in battles with the Andhras and Gaudas, and the Guptas of Magadha?

<p>Expanding territorial control and extracting tribute from defeated rivals, augmenting the kingdom's resources and influence. (C)</p> Signup and view all the answers

Given that Adiya Vardhan, Rajya Vardhan, and Nara Vardhan of the Pushyabhuti dynasty held the title 'Maharaja', but Prabhakara Vardhan adopted the title 'Param Bhattarak Maharajadhiraja', what profound transition in the dynasty's standing does this title change BEST illustrate?

<p>Evolution from regional power to imperial sovereignty, reflecting increased military prowess and territorial expansion. (A)</p> Signup and view all the answers

Flashcards

Post-Gupta Kingdoms

Kingdoms that emerged after the Gupta empire disintegrated in the 6th century AD.

The Maukharis

A dynasty that rose to prominence after the Gupta empire; their capital was Kannauj.

Maharaja Title

Title given to the first three kings of the Maukhari dynasty.

Ishana Varman

The 4th king of the Maukhari dynasty (550-560 AD) who declared himself Maharajadhiraja.

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Sarva Varman

A Maukhari ruler who took the throne from Ishana Varman.

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Graha Varman

A significant Maukhari ruler who married Rajyashri of the Pushyabhuti family.

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The Pushyabhutis

Dynasty of Thaneshwar that rose to prominence post-Gupta.

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Prabhakara Vardhan

First king of the Pushyabhuti dynasty, who took the title 'Param Bhattarak Maharajadhiraja'.

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Hunas and Gurjaras

Dynasties overpowered by Prabhakara Vardhan.

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Rajya Vardhan

King who replaced Prabhakar Vardhan but was killed in battle.

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Harsha Vardhana

Took the throne after Rajya Vardhan's death with the support of the Mantri Parishad.

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Hieun-Tsang's Writings

Writings that improved the understanding of Harsha's reign.

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'Siladitya'

Name assumed by Harsha, meaning 'Sun'.

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Prayag and Kanauj assemblies

Two important assemblies that took place during Harsha's reign.

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Study Notes

  • Stability in closed loop systems can be determined by analyzing the open loop transfer function, denoted as G(s).
  • Stability assessment involves determining the number of unstable poles using the frequency response of G(s).

Example Scenario

  • G(s) = 1/(s-1) represents an open loop transfer function.
  • H(s) = G(s) / (1 + G(s)) = 1/s illustrates the closed loop transfer function, which in this case is stable even though the open loop system is unstable.

Nyquist Plot Overview

  • It is a graphical representation of G(jω) on the complex plane across the frequency range of negative infinity to positive infinity.
  • Plotting from 0 to positive infinity is sufficient due to the property G(jω) = G(-jω)* and the plot is then completed based on symmetry.
  • The Nyquist plot allows deduction of the stability of a closed loop system.

Nyquist Criterion Explained

  • N is defined as the number of clockwise encirclements of the -1 point by the Nyquist plot of G(s).
  • P is the number of unstable poles in G(s), which represents the open loop system.
  • Z is the number of unstable poles in the closed loop system, represented by G(s) / (1 + G(s)).
  • The relationship between these variables is given by Z = N + P.
  • Closed loop system achieves stability if and only if N = -P.

Nyquist Criterion Considerations

  • A "Nyquist contour" is needed; use a semi-circle of infinite radius (R → ∞) enclosing the right half of the complex plane.
  • Indentations around poles on the imaginary axis are necessary if present in G(s).

Applying the Nyquist Criterion - Example

  • Consider G(s) = 1/(s-1).
  • Nyquist contour includes the pole at s = 1.
  • Semi-circle at infinity maps to the origin.
  • If the Nyquist plot encircles -1 once clockwise, then N = 1.
  • Given P = 1, Z = N + P = 1 + (-1) = 0, indicating the closed loop system is stable.

Robust Stability

  • Assumes models are not perfectly accurate due to uncertainties.
  • Controllers should be designed to maintain stability despite these uncertainties across a range of plant models.

Uncertainty Types

  • Unstructured uncertainty indicates limited knowledge about the model inaccuracies:
    • Additive uncertainty represents the transfer function as G(s) + W(s)Δ(s).
    • Multiplicative uncertainty represents the transfer function as G(s)(1 + W(s)Δ(s)).
    • Here, Δ(s) is any stable transfer function where the infinity norm of Δ(s) is less than or equal to 1 (||Δ(s)||_∞ ≤ 1).
    • W(s) is a weighting function adjusting for the frequency content of the uncertainty.
  • Structured uncertainty indicates partial knowledge, such as a pole or zero.

Robust Stability Assessment

  • For multiplicative uncertainty G(s) → G(s)(1 + W(s)Δ(s)).
  • The closed loop transfer function is T(s) = G(s) / [1 + G(s)K(s)].
  • A sufficient condition to maintain stability for all Δ(s) where ||Δ(s)||∞ ≤ 1 requires the infinity norm of W(s)T(s) to be less than 1 (||W(s)T(s)||∞ < 1).

Robust Stability - Example

  • System specified by G(s) = 1/(s+1) and K(s) = 1.
  • Uncertainty weighted by W(s) = (0.5s) / (s+2).
  • Closed loop transfer function then is T(s) = 1 / (s+2).
  • Ensuring robust stability requires ||W(s)T(s)||_∞ = sup over ω |W(jω)T(jω)| and that this result must be less than 1.

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