High precision motion control of parallel robots with imperfections and manufacturing tolerances

This work attempts to achieve precise motion control using parallel robots with manufacturing tolerances and inaccuracies by migrating the measurements from their joint space to task space in order to decrease control system’s sensitivity to any kinematical uncertainty rather than calibrating the parallel plant. The problem of dynamical model uncertainties and its effect on the derivation of the control law is also addressed in this work through disturbance estimation and compensation. Eventually, both task space measurement and disturbance estimation are combined to formulate a control framework that is unsensitive to either kinematical and dynamical system uncertainties

Sensorless torque estimation in multidegree-of-freedom flexible systems

This paper presents a sensorless torque estimation algorithm for multidegree-of-freedom flexible systems. The proposed algorithm makes it possible to estimate externally applied torques due to flexible system s interaction with the environment without taking any measurement from the system. The algorithm is based on modifying the disturbance observer in order to decouple the reflected torque waves out of the total disturbance on the actuator. Then Reflected torque waves are used along with the actuator s current and velocity to estimate flexible system parameters, dynamics and the external torques or disturbances. Several experimental results are included in order to confirm the validity of the proposed torque estimation algorithm

A content-aware quantisation mechanism for transform domain distributed video coding

The discrete cosine transform (DCT) is widely applied in modern codecs to remove spatial redundancies, with the resulting DCT coefficients being quantised to achieve compression as well as bit-rate control. In distributed video coding (DVC) architectures like DISCOVER, DCT coefficient quantisation is traditionally performed using predetermined quantisation matrices (QM), which means the compression is heavily dependent on the sequence being coded. This makes bit-rate control challenging, with the situation exacerbated in the coding of high resolution sequences due to QM scarcity and the non-uniform bit-rate gaps between them. This paper introduces a novel content-aware quantisation (CAQ) mechanism to overcome the limitations of existing quantisation methods in transform domain DVC. CAQ creates a frame-specific QM to reduce quantisation errors by analysing the distribution of DCT coefficients. In contrast to the predetermined QM that is applicable to only 4x4 block sizes, CAQ produces QM for larger block sizes to enhance compression at higher resolutions. This provides superior bit-rate control and better output quality by seeking to fully exploit the available bandwidth, which is especially beneficial in bandwidth constrained scenarios. In addition, CAQ generates superior perceptual results by innovatively applying different weightings to the DCT coefficients to reflect the human visual system. Experimental results corroborate that CAQ both quantitatively and qualitatively provides enhanced output quality in bandwidth limited scenarios, by consistently utilising over 90% of available bandwidth

Control systems with network delay

In this paper motion control systems with delay in measurement and control channels are discussed and a new structure of the observer-predictor is proposed. The feature of the proposed system is enforcement of the convergence in both the estimation and the prediction of the plant output in the presence of the variable, unknown delay in both measurement and in the control channels. The estimation is based on the available data – undelayed control input, the delayed measurement of position or velocity and the nominal parameters of the plant and it does not require apriori knowledge of the delay. The stability and convergence is proven and selection of observer and the controller parameters is discussed. Experimental results are shown to illustrate the theoretical prediction

Optimal motion control and vibration suppression of flexible systems with inaccessible outputs

This work addresses the optimal control problem of dynamical systems with inaccessible outputs. A case in which dynamical system outputs cannot be measured or inaccessible. This contradicts with the nature of the optimal controllers which can be considered without any loss of generality as state feedback control laws for systems with linear dynamics. Therefore, this work attempts to estimate dynamical system states through a novel state observer that does not require injecting the dynamical system outputs onto the observer structure during its design. A linear quadratic optimal control law is then realized based on the estimated states which allows controlling motion along with active vibration suppression of this class of dynamical systems with inaccessible outputs. Validity of the proposed control framework is evaluated experimentally

Nutritional value of Pleurotus (Flabellatus) Djamor (R-22) cultivated on sawdusts of different woods

The sawdust of different woods were investigat ed for the cultivation of exotic strain of Pleurotus (flabellatus) djamor (R-22) to find out the efficiency of different nutrients including protein, fat, crude fiber, ash, dry matter and moisture. Among all type of nutrients, protein, fat, cr ude fiber, ash, dry matter and moisture of Pleurotus ostreatus on sawdust of different woods were observed. Protein was observed on cont rol treatment (cotton waste, kikar, mango, mixed sawdust, simbal and kail (21.89), (21.64), (21.34), (21.16), (21.03) and (20.75) % respectively. Fat was observed on control treatment (cotton waste, kikar, mango, mi xed sawdust, simbal and kail (0.80), (0.53), (0 .41), (0.33), (0.24) and (0.11)% respectively. Crude fiber was observed on control treatment (cotton waste, kikar, mango, mixed sawdust, simbal and kail (8.92), (8.45), (8.17), (7.96), (7.70) and (7.32) % respectively. Ash was observ ed on control treatment (cotton waste, kikar, mango, mixed sawdust, simbal and kail (7.65), (6.75), (6 .47), (6.39), (6.33) and (6.23%) respectively. Dry matter was observed on control treatment (cotton waste, kikar, mango, mixed sawdust, simbal and kail (6.47), (6.27), (6.13), (6.01), (5.87) and (5.67) % respectively. Moisture was observed on control treatment (c otton waste, kikar, mango, mixed sawdust, simbal and kail (84.55), (81.20), (79.85), (76.26), (74.35) and (71.14) % respectively. Oyster mushroom showed relatively more contents on control treatment cotton waste as compared to other substrates. The maximum protein, fat, crude fiber, ash, dry matter and moisture contents in Pleurotus (flabellatus) djamor (R-22) was obtained on Kikar sawdust .The lowest contents was obtained on kail sawdust